INTRODUCTION TO HYGIENE. METHODS OF HYGIENIC RESEARCH. ORGANIZATION
OF EDUCATIONAL AND SCIENTIFIC RESEARCH.
HYGIENE
AIR ENVIRONMENT. DEFINITION AND HYGIENIC EVALUATION OF TEMPERATURE, HUMIDITY, ATMOSPHERIC PRESSURE, DIRECTION AND SPEED
OF AIR MOVEMENT. HYGIENIC REQUIREMENTS FOR HEALTH
IMPROVEMENT PHARMACIES.
HYGIENIC ASSESSMENT OF ILLUMINATION. HYGIENIC
REQUIREMENTS FOR HEALTH IMPROVEMENT PHARMACIES.
Health - is defined
as a state of complete physical, mental and social well-being and not merely
absence of disease or infirmity.
Health is the functional
and/or metabolic efficiency of an organism, at any moment in time, at both the
cellular and global levels. All individual organisms, from the simplest to the
most complex, vary between optimum health and zero health (dead).
Perfect health is an abstraction, which may not
be attainable but is essential for an individual or a family or a group
or a community's strivings. Optimum Health is the highest level of health
attainable by an individual in his/her ecological settings. Positive health
means striving for preservation and improvement of health. Negative health
means scientific efforts for prevention and cure of diseases. To promote and
maintain a state of positive health an individual needs the following
prerequisites:
· Supply
of fresh air and sunlight
· Safe
and potable water supply
· Balanced
diet
· Healthful
shelter
· Adequate
clothing hygienic environmental sanitation
· Protection
from communicable and other avoidable afflictions
· Complete
sense of protection and security both socially and economically
· A
congenial social and cultural atmosphere.
· In
addition an individual should have a regulated way of life with proper rest and
relaxation and good and simple habits.
All these factors help to maintain a normal
balance of body and mind, which is must for positive health. The study of all
these factors constitutes a branch of medicine designated as preventive and
social medicine. Any imbalance or deviation in the above factors is likely to cause
a state of illness, when curative aspect of medicine comes into picture.
Hygiene - is a basic preventive science in medicine. It
generalizes all dates of theoretical and clinical disciplines in the field of
prophylaxis, integrates knowledge’s about complex influence of an environment
for health of the man, work out principles and systems of preventive measures.
The
word Hygiene is derived from the Greek
word (Hygeia) Hygieia — the
goddess of health.
In Greek
mythology, Hygieia (Roman
equivalent: Salus) was a daughter of Asclepius.
She was the goddess of health, cleanliness and sanitation (and later: the
moon), and played an important part in her father's cult (see also: asklepieion).
While her father was more directly associated with healing, she was associated
with the prevention of sickness and the continuation of good health.
Hygiene is defined as the science and
art of preserving and improving health. Hygiene deals both with an individual
and a community as a whole. Personal Hygiene is the term used for improvement
of hygiene of an individual or a person. Social Hygiene is usually the term
used for dealing with problems of sex especially for control of venereal
diseases. Similarly other terms like mess hygiene, milk hygiene, hygiene of
feeding, hygiene of clothes, hygiene of infant feeding etc., are self-explanatory
Hygiene and Good Habits are
commonly understood as preventing infection
through cleanliness.
In broader call, scientific terms hygiene is the maintenance of health and
healthy living. Hygiene ranges from personal hygiene, through domestic up to occupational hygiene and public health;
and involves healthy diet, cleanliness, and mental health.
What is pollution.htm
Environmental Sanitation
The word Sanitation - is derived from the Latin word Sanitas
which means a state of health. Environmental Sanitation means the control of
all those factors in man's surroundings, which cause or may cause adverse
effects on his health. The sanitarian directs his efforts towards hygiene of
water and food supply, hygienic disposal of human wastes, hygiene of housing
and control of vectors and rodents etc.
The following definition now is accepted:
«Hygiene is a science, which investigates regularities of influence of the
environment on the organism of the man and public health with the purpose of
the substantiation of the hygienic norms, sanitarian rules and measures,
realization of which will ensure optimum conditions for vital activity,
improving of health and preventing of diseases ».
The principal topics of
the subject are:
· Hygiene of atmospheric
air
· Water supply hygiene
· Hygiene of nutrition
· Occupational hygiene
· Radiological hygiene
· Hygiene of children and
teenagers
· Hospital hygiene
· Hygiene of extraordinary
situation
· Tropical hygiene
Hygiene is a science of
preserving and promoting the health of both the individual and the community.
It has many aspects:
Ø
personal hygiene (proper living habits, cleanliness of body and
clothing, healthful diet, a balanced regimen of rest and exercise);
Ø
domestic hygiene (sanitary
preparation of food, cleanliness, and ventilation of the home);
Ø
public hygiene (supervision of water and food supply, containment
of communicable disease, disposal of garbage and sewage, control of air and water
pollution);
Ø
industrial hygiene (measures that
minimize occupational disease and accident);
Ø
mental hygiene (recognition of mental and emotional factors in
healthful living) and so on.
2. THE AIM AND TASKS OF
HYGIENE
Basic aim of hygiene
Preservation
and improving the health of the man is a basic aim of hygiene.
In
this occasion the English scientist E.Parce has told, that the hygiene has a
great and generous purpose: «...To make development of the man most perfect,
life most intense, wasting least fast, and death most remote».
The tasks of a hygienic science:
1. Study of the natural and
anthropogenesis factors of the environment and social conditions which
influence on health of the man.
2. Study regularities of
influence the factors and conditions of an environment on an organism of the
man or population.
3. Scientific substantiation
and working out of the hygienic norms, rules and measures, which help use
maximum positively influencing on an organism of the man the factors of an
environment and elimination or restriction up to safe levels unfavourable
operating ones.
4. Introduction in practice of
public health services and national economy developed hygienic recommendations,
rules and norms check of their effectiveness and perfecting.
5. Prediction of the sanitarian situation
for the nearest and remote perspective in view of plans of development of the
national economy. Definition of appropriate hygienic problems, which implying
from prognostic situation and scientific working out these problems.
3. BASIC METHODS OF HYGIENIC RESEARCHES
During the development the hygiene used many
methods of study an environment and its influence on the health of the
population.
Methods
of hygiene
1. Methods of
environment studying.
2. Methods of
studying of environmental influence on human organism and health
1. Methods of environment studying
Methods of sanitary examination with further sanitary description
Speaking
about methods of the research the exterior factors, first of all it is
necessary point at method sanitarian description, which for a long time being
almost only. It did not lost the value and now.
Specific
hygienic method is method of sanitary examination and describing which
is used for studying the environment.
Sanitary examination and describing is carried
out according to special programs (schemes), which contain questions. Answers
to these questions characterize the object, which is being examined hygienically.
As a rule it is usually supplemented by laboratory analyses (chemical,
physical, microbiological and other), which allows characterizing environment
from the qualitative side.
Instrumental and laboratory methods With the help of physical methods we can study microclimatic conditions,
electrical conditions of air, all aspects of radiant energy, mechanical and
electromagnetic oscillation, carry out the spectroscopic analysis and much
other.
By chemical methods we can
determine peculiarities of a natural structure of all elements of an
environment, the quantitative and qualitative indexes of it contamination,
enable to make conclusion about sanitarian troubles of the investigated object.
The biological methods, first of all
bacteriological researches, for example, definition of a credit of the
Esherichia colli, have much value for conclusion about epidemiological safety
of the potable water.
THE
METHOD OF DETERMINATION AND HYGIENIC ESTIMATION OF AIR TEMPERATURE AND
ATMOSPHERIC PRESSURE
Air temperature is a measure of how
hot or cold the air is. It is the most commonly measured weather parameter.
More specifically, temperature describes the kinetic energy, or energy of
motion, of the gases that make up air. As gas molecules move more quickly, air
temperature increases.
Why is Air Temperature Important?
Air temperature affects
the growth and reproduction of plants and animals, with warmer temperatures promoting
biological growth. Air temperature also affects nearly all other weather
parameters. For instance, air temperature affects:
- the rate of evaporation
- relative humidity
- wind speed and direction
- precipitation patterns and types, such as whether it will rain,
snow, or sleet.
How is Air Temperature measured?
Temperature is usually expressed in
degrees Fahrenheit or Celsius. 0 degrees Celcius is equal to 32 degrees
Fahrenheit. Room temperature is typically considered 25 degrees Celcius, which
is equal to 77 degrees Fahrenheit.
A more scientific way to describe
temperature is in the standard international unit Kelvin. 0 degrees Kelvin is
called absolute zero. It is the coldest temperature possible, and is the point
at which all molecular motion stops. It is approximately equal to -273 degrees
Celcius and -460 degrees Fahrenheit.
TEMPERATURE SCALES
Temperature is a physical quantity that is a measure of
hotness and coldness on a numerical scale. It
is a measure of the local thermal energy of matter or radiation; it is measured by a thermometer, which may becalibrated
in
any of various temperature scales,
Celsius, Fahrenheit, Kelvin, etc., etc.
Much
of the world uses the Celsius scale
(°C) for most temperature measurements. It has the same incremental scaling as
the Kelvin scale
used by scientists, but fixes its null point, at0°C = 273.15K,
approximately the freezing point of water (at one atmosphere of pressure).[note 1] The
United States uses the Fahrenheit scale
for common purposes, a scale on which water freezes at 32 °F and boils at
212 °F (at one atmosphere of pressure).
For
practical purposes of scientific temperature measurement, the International System
of Units (SI) defines a scale and unit for the
thermodynamic temperature by using the easily reproducible temperature of
the triple point of
water as a second reference point. The reason for this choice is that, unlike
the freezing and boiling point temperatures, the temperature at the triple
point is independent of pressure (since the triple point is a fixed point on a
two-dimensional plot of pressure vs. temperature). For historical reasons, the
triple point temperature of water is fixed at 273.16 units of the measurement
increment, which has been named the kelvin in honor of the Scottish physicist
who first defined the scale. The unit symbol of the kelvin is K.
Absolute
zero is defined as a temperature of precisely 0 kelvins,
which is equal to −273.15 °C or −459.67 °F.
One
of the earliest temperature scales was devised by the German physicist Gabriel Daniel Fahrenheit. According
to this scale, at standard atmospheric pressure, the freezing point (and
melting point of ice) is 32° F, and the boiling point is 212° F. The centigrade, or Celsius scale,
invented by the Swedish astronomer Anders Celsius, and used throughout most of
the world, assigns a value of 0° C to the freezing point and 100° C to the
boiling point.
http://www.ux1.eiu.edu/~cfadd/1360/19Temp/Absolute.html
In
scientific work, the absolute or Kelvin
scale, invented by the British mathematician and physicist William
Thomson, 1st Baron Kelvin, is used. In this scale, absolute zero is at -273.16°
C, which is zero K, and the degree intervals are identical to those measured on
the Celsius scale. The corresponding “absolute
Fahrenheit” or Rankine scale, devised by the British engineer and
physicist William J. M. Rankine, places absolute zero at -459.69° F, which is
0° R, and the freezing point at 491.69° R. A more consistent scientific
temperature scale, based on the Kelvin scale, was adopted in 1933.
An
absolute temperature scale invented in the 1800's by William Thompson, Lord
Kelvin. It places the zero point of the scale at absolute zero, the temperature
which scientists believe is the lowest possible. All molecular motion would
stop there. A Kelvin degree is the same size as a Celsius degree, so the two
scales simply have a constant offset.
Temperature.
An
instrument called thermometer ascertains this.
Generally mercury or
alcohol is used in the thermometers. Mercury is used in thermometers meant for recording high temperatures on account of its uniformity in expansion at different
temperatures, easy visibility, high boiling point and low vapor pressure. Alcohol is used in thermometers for recording low temperatures, because it does not freeze even at low temperatures. Several
kinds of thermometers are used
These are:
(1)Standard
or Dry Bulb Thermometer. It is an ordinary
thermometer.
(2)Maximum
Thermometer. It is used for registering the highest temperature attained in the day or any other period. The thermometer
is laid in a horizontal
position. In the stem of the thermometer, part
of the mercury column is separated by air. When the temperature rises the mercury expands and pushes this broken column forward.
But this column does
not recede when the temperature falls and the main mercury column contracts.
The reading taken
indicates the maximum temperature attained during the day.
(3)
The Minimum Thermometer. It is used for recording the lowest
temperature during the night or during the early hours of morning. A small glass index is enclosed in the spirit, which fills the bulb and a part of the stem. When setting the instrument, the index is first brought to the top of the column of the spirit and the instrument is placed in a horizontal position. When the temperature rises, the spirit expands and flows past the index, but when the temperature falls, the spirit contracts and carries the index along with it. The lowest temperature is thus registered. The instrument can be readjusted by tilting.
(4) Six's Maximum and Minimum Thermometer. It is a combination of maximum and minimum thermometers and gives a double reading. It is however, not a very accurate instrument and is therefore no more being used now
in Indian Meteorological
observatories.
Methods
of temperature measure
On
value of temperature regime on the room measure do in difference place on a
vertical.
First measure of temperature is done on 10 cm from the
floor and characterizes air on foot level.
Second measure do on 1,5 meter from the floor – in respiration zone
of man.
Third
place is on 50 cm
from ceiling and characterizes convection in the room. In hospital the second
place is situated on level of bad. Measuring of temperature in horizontal line
is done in three points: from external angle to internal angle on 20 cm. Change
of temperature in time is measured by thermograph. It’s done in three places
on 1,5 cm from the floor.
Thermometer
It
is instrument used to measure temperature. The invention of the thermometer is
attributed to Galileo, although the sealed thermometer did not come into
existence until about 1650. The modern alcohol and mercury thermometers were
invented by the German physicist Gabriel Fahrenheit, who also proposed the
first widely adopted temperature scale, named after him.
Types
of thermometers
•Wide
variety of devices are employed as thermometers. The primary requirement is
that one easily measured property, such as the length of the mercury column,
should change markedly and predictably with changes in temperature.
•Electrical
resistance of conductors and semiconductors increases with an increase in temperature. For thermistor of given
composition, the measurement of specific temperature will induce specific
resistance. This resistance can be measured by galvanometer and becomes measure
of the temperature. With proper circuitry, the current reading can be converted
to a direct digital display of the temperature.
Very
accurate temperature measurements can be made with thermocouples in which small voltage difference (measured in
millivolts) arises when two wires of dissimilar metals are joined to form a
loop, and the two junctions have different temperatures.
•Optical
pyrometer is used to measure
temperatures of solid objects at temperatures above 700° C (about 1300° F)
where most other thermometers would melt. At such high temperatures, solid
objects make so-called glow color phenomenon. The color at which hot objects
glow changes from dull red through yellow to nearly white at about 1300° C
(about 2400° F). The pyrometer contains a light bulb type of filament
controlled by a rheostat (dimmer switch) that is calibrated so that the colors
at which the filament glows corresponding to specific temperatures.
•Another
temperature-measuring device, used mainly in thermostats, relies on the differential thermal expansion between
two strips or disks made of different metals and either joined at the ends or
bonded together.
Special
types of thermometers
Thermometers
may also be designed to register the maximum or minimum temperature attained.
•Maximum
thermometers.A mercury-in-glass clinical thermometer, for
example, is maximum-reading instrument in which trap in the capillary tube
between the bulb and the bottom of the capillary permits the mercury to expand
with increasing temperature, but prevents it from flowing back unless it is
forced back by vigorous shaking.
•Minimum
thermometers. Inside capillary tube is alcohol with glass
pin. When temperature increase ethanol moves pin. When temperature decrease
ethanol paces pin for a minimal temperature.
Thermograph.
•Thermograph
consists of vertical pen, bimetallic laminas and clack mechanism. Perceiving
part of instrument is bimetallic laminas, which change it curvature by change
of temperature. By means system of levers which passes changing curvature of
bimetallic laminas by righting pen and we have graphical illustration of
temperatures on paper of clack mechanism.
Table
of Equivalent Temperatures by Celsius and Fahrenheit scales
C
= (F - 32) х 100/180;
F
= (C х 180/100) + 32.
Measuring
Maximum and Minimum temperature
If
possible it is best to record the daily maximum and minimum temperature as well
as that which you record at a specific moment in time when you make your
observations. You can simply use your normal thermometer. With this you need to
record temperatures at about 14:00 where the daily maximum usually occurs, or
very early morning when the temperature is similar to the overnight minimum. These
are good times to take your am/pm measurements.
Studying
the temperature condition of the indoor air
The
temperature is measured in 6 or more points to fully characterize the
temperature conditions of premises.
Thermometers
(mercurial, alcohol, electric or psychrometer dry thermometers) are placed onto
support racks at three points 0.2 meter high above the floor, at three points
1.5 meters high (points t2, t4, t6 and t1,
t3, t5 respectively) and at 20 cm from the wall along the
diagonal section of the laboratory according to the diagram:
The
thermometer data are fixed after 10 minutes of the exposition at the point of
measurement.
The
air temperature parameters in premises are calculated using following formulas:
а) the average temperature in the
premises:
а) taver.= ,
b)
the vertical variation of the air temperature:
D
c)
the horizontal variation of the air temperature:
D
Diagrams
and calculations are written down into the protocol, the hygienic assessment is
made. It is necessary to consider the following data: the optimal air
temperature must be from +18 to +21оС in
residential and class-room premises, wards for somatic patients, the vertical
temperature variation must be no more than 1.5-2.0оС, horizontal - no more than 2.0-3.0оС. The daily temperature variations are determined using the thermogram,
prepared in laboratory using the thermograph. The daily temperature variation
must be no more than 6оС.
The
allowable and optimal standards of the temperature, presented in the table 1
are the hygienic assessment criteria for residential and public premises.
Table
1
The
temperature standards for residential, public and administrative premises
Comment:
* the allowable
temperature is no more than 28оС for public and administrative premises, which are
permanently inhabited, for regions with the estimated outdoor air temperature
of 25оС and above – no more than 33оС.
** the allowable
temperature is 14оС for public
and administrative premises where the inhabitants are wearing their street
clothes.
The
standards were established for people that are continuously staying in the
premises for 2 hours or more.
The
temperature standards for the workplace air of industrial areas are set in the
State Standard #12.1.005-88 “General sanitary and hygienic requirements to the
workplace air”, depending on the season (cold, warm) and work category (easy,
moderate and hard).
The
optimal temperature standards for the cold season are set from 21 to 24оС during the physically easy work and from
16 to 19оС during the physically hard work.
These temperature ranges correspond to 22-25оС and 18-22оС during the warm season. The
allowable maximum temperature is no more than 30оС for the warm season, the allowable minimum temperature for the
cold season is 13оС.
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding
temperature is very different. This process is one aspect of homeostasis: a dynamic state
of stability between an animal's internal environment and its external environment (the study of such
processes in zoology has been called ecophysiology or physiological ecology). If the body is unable to
maintain a normal temperature and it increases significantly above normal, a
condition known as hyperthermia occurs. For humans, this occurs when the body is
exposed to constant temperatures of approximately 55 °C (131 °F), and any prolonged
exposure (longer than a few hours) at this temperature and up to around 75 °C (167 °F) death is almost inevitable. Humans
may also experience lethal hyperthermia when the wet bulb temperature is sustained above 35
°C (95 °F) for six hours. The opposite condition, when body
temperature decreases below normal levels, is known as hypothermia.
The
radiant temperature and the wall temperature determination
The
spherical thermometers are used for the radiant temperature determination in
premises, wall thermometers – for the wall temperature determination (see fig.
6.1 а, b)
The
spherical thermometer consists of the thermometer located inside the hollow
sphere 10-15 cm in diameter and covered with porous polyurethane foam layer.
This material has similar coefficients of the infrared radiation adsorption as
the human skin.
The
radiant temperature is also determined at 0.2 and 1.5 meters above the floor.
The
device has the considerable inertia (up to 15 min.), that is why the
thermometer data must be taken no earlier than after that time.
The
spherical thermometer data at the height of 0.2 and 1.5 m must not vary by more
that 3оС in comfortable microclimate
conditions.
Fig.
6.1. Thermometers for the radiant temperature determination
a
– the section of the spherical black thermometer
(1 – 15 cm diameter sphere covered
with dull black paint; 2 – thermometer with the reservoir at the center of the
sphere)
b
– Wall thermometer with the flat turbinal reservoir
(1 – thermometer; 2 – base cover
(foam-rubber); 3 –sticky tape)
The
values of the radiant temperature below are recommended for different premises
(see table 2).
Table
2
Standard
values of radiant temperature for different premises
Special
thermometers with the flat turbinal reservoir are used for the wall temperature
determination. These thermometers are attached to the wall with special putty
(wax with colophony addition) or alabaster. The wall temperature is also
determined at 0.2 and 1.5 meters above the floor. In some cases it is necessary
to determine the temperature of coldest parts of the wall.
The
high levels of infrared irradiation in especially hot manufacture areas are
measured using actinometers (solar radiation instrument) and are expressed in
mcal/(сm2×min).
Water
vapor
The
person during all life is exposed to water vapor. Its quantity in air
permanently changes: it decreases or increases. When in air a lot of water
vapor is stored, the conditions for evaporation of moisture are worse. In air
such quantity of water vapor can be stored, that it resilience equals
resilience of liquid that evaporates, - and then the evaporation ceases.
The
evaporation depends on temperature of air, the above last, the implements
evaporation fan-in harder. There fore evaporation as though goes after
temperature of air; temperature of air - is increased the evaporation is
increased also; temperature of air is lowered, the evaporation is lowered also.
Air
humidity
Humidity is moisture content of the atmosphere. The
atmosphere always contains some moisture in water vapor; the maximum amount
depends on the temperature. The amount of vapor that will saturate the air
increases with temperature rise. At 4.4° C (40° F), 454 kg (1000 lb) of moist air contain maximum
2 kg of water vapor; at 37.8° C (100° F), the same amount of moist air contains
maximum 18 kg of water vapor. When the atmosphere is saturated with water, the
level of discomfort is high because the evaporation of perspiration, with its
attendant cooling effect, is impossible.
Humidity is specified in several different ways.
The weight of water vapor contained in a volume of air is known as the absolute
humidity and is expressed in grams of
water vapor per cubic meter.Relative humidity, given in weather forecasts, is the ratio between the actual content of the air vapor and the
content of the air vapor at the
same temperature saturated with water vapor.
The
maximum damp is measured by that quantity of a water pair in grammas, which one
saturates completely 1m3 of air at given temperature
The
relative humidity is an attitude of absolute humidity to maximum at given
temperature, expresses in percentage, that is:
R=A
/ F х 100,
Where
R - relative humidity;
•A-
absolute humidity;
•F
- maxime humidity.
The
relative humidity interests us because its characterize saturation of air by a pair, its dryness. For
example, if we speak, that relative humidity 60 %, from this number it is
visible, that 40 % of a moisture does not suffice to saturation of air, that
is, it has a capability to receive a moisture. At relative humidity 80 % we
could say, that in this case elasticity of a pair in atmosphere is higher, at
her the liquid evaporates worse. At 90 % - it is even worse.
Knowing absolute humidity it is possible to
definite dew point, that is that temperature, at which one the absolute
humidity becomes maximum and the air humidity will begin to be condensate and
to precipitate by the way of drops of water. Let's consider such example. What
the temperature this damp will begin to saturate air? It also means to find dew
point.
The
air humidity can be described as deficit of saturation. The deficit of
saturation is a difference between maximum and absolute humidity at same
temperature. Together with it there is also concept a physiological deficit of
saturation. It - difference between maximum damp at the temperature of bodies
of the person 36,5 degree and absolute humidity of air.
The
most commonly used measure of humidity is relative humidity.
Relative humidity can be simply defined as the amount of water in the air
relative to the saturation amount the air can hold at a given temperature
multiplied by 100. Air with a relative humidity of 50% contains a half of the
water vapor it could hold at a particular temperature.
Figure
-1 illustrates the concept of relative
humidity.
The
following illustration describes how relative humidity changes in a parcel of
air with an increase in air temperature. At 10° Celsius, a parcel of dry air weighing
one kilogram can hold a maximum of 7.76 grams of water vapor
Physiological
relative humidity
Hygiene
uses also concept of physiological relative humidity. It is attitude of
absolute humidity at given temperature of air to maximum at 36,5 degree,
expressed in percentage. Physiological relative humidity characterizes
capability of air to accept damp that evaporates at body temperature. It enables
more precisely to evaluate effect of moist air.
Air
humidity can be described as deficit of saturation. The deficit of saturation
is difference between maximum and absolute humidity at same temperature.
There
is also a concept of physiological deficit of saturation. It is difference
between maximum damp at body temperature person 36,5 degree and absolute
humidity of air. The physiological deficit of saturation lets us define how
many grams of water the person can spend by evaporation in given conditions.
Air
humidity is very relevant hygienic
factor because it influences thermo exchange of the person. At low temperatures
in moist air the feeling of cold is stronger than in dry air at the same
temperature.
It
is by outcome that the moist air has large heat conductivity and thermal
capacity. From the same reason in wet clothes it is much more cold: pores of
tissues charged with moisture, and its well carries out heat.
Human
body permanently loses moisture either by water vapor or by liquid water. It is
established that in quiet condition at room temperature the person loses by
skin approximately 20% of moisture, mild - 15 %, remaining part - urine and
feces. Therefore, in these conditions approximately 35% of water is lost by
evaporation and 65% - in liquid with feces and urine. By activity and heat of
air – in the contrary: 60% of water is lost by evaporation from skin and mild
and much less by urine and feces.
Normal
relative air humidity in dwelling apartments is 30-60%. A great range of normal
air humidity is explained fluctuations by the fact , that its influence on the
organism depends on a number of conditions. In peace when the air temperature
is 16-200С with a light air motion the optimum humidity will be 40 -
60%. During physical work when the air temperature is above 200С or
below 150С air humidity must not be more than 30-40%, and when the
temperature above 25 0С desirable to bring relative humidity down to
20%.
Air
humidity determination methods
Humidity
is determined by psychrometes and hygrometers. Hygrographs determine humidity
fluctuations for a day or a week. Absolute air humidity is determined by
psychrometes (from greek psychros - cold).Psychrometes are of August and Assman
types.
August
psychrometer consists of two identical mercury thermometers fixed on a
support. By temperature difference on dry and humid thermometers we can define
absolute air humidity with a help of table or formula.
Assman
psychrometer consists of dry and humid thermometer situating in metal casing
that protects from radiation temperature. There is a ventilator in the upper
part of the device. Ventilator is wound up and during 5 minutes in summer (15
minutes in winter) registers a temperature difference.
Relative
humidity is measured by hygrometer.
It consists of metal frame in the middle of which a fair defatted woman’s hair
is lightened. When humidity is low the hair becomes shorter, when it is high it
becomes longer.
Instruments
to Measure Humidity
A
whirling psychrometer is a type
of hygrometer which can be whirled around like a football rattle to take
readings. You can directly read off the percentage relative humidity. It is a
good idea to wrap it in a damp cloth for a while and then set the dial to read
100 %. Like paper, human hair stretches when moist and shrinks when dry.
Humidity recorders use this principle, and you can make a simple hygrometer
using this method.
http://www.piercecollege.com/offices/weather/psychrometer.html
The
Psychrometer measures the wet and dry bulb temperature and under natural
evaporation conditions the state of a given mass of air can be described by its
temperature and vapor pressure. If water is allowed to evaporate in an isolated
mass of unsaturated air , it latent heat content increases and its sensible
heat content decreases. The process will stop when the air becomes saturated at
the wet bulb temperature ( Tw). The change in latent heat must equal the change
in sensible heat. http://weather.nmsu.edu/Teaching_Material/soil698/psych.html
A
pair of thermometer placed parallel inside the screen with a bare bulb on the
right indicating the air temperature and is called dry bulb thermometer.
Another thermometer on the left whose blackened globe is covered with a
moistened muslin wick is called wet bulb thermometer. Since they are usually
using in a pair, therefore, we normally call them psychrometer.
The
absolute humidity is calculated using the Regnault formula:
А = f – a · (t - t1) ·
B,
where,
А – the air absolute humidity
at the current temperature in Hg mm;
f – maximum pressure of water
vapour at the wet thermometer’s temperature (see the table of saturated water
vapours, table 3);
а – psychrometric coefficient is 0.0011 for
enclosed spaces;
t – temperature of the dry thermometer;
t1 – temperature of the wet
thermometer;
В – barometric pressure during the humidity
determination, Hg mm.
The
relative humidity is calculated using the following formula:
P = ,
where, Р
–the value of relative humidity to be found, %;
А – absolute humidity, Hg mm;
F – maximum pressure of water
vapour at the dry thermometer temperature, Hg mm (see the table of saturated
water vapours, table 3).
Table
3
Psychrometric
tables for the August psychrometer are used for the relative humidity (RH)
determination (if the air velocity is 0.2 m/sec.). The value of RH is found at
the point of the dry and wet thermometers data intersection, table 4.
The
psychrometer operation is based on the fact that the rate of the water
evaporation from the surface of dampened psychrometer’s reservoir is
proportional to the air dryness. The drier the air – the lower is the wet
thermometer’s result in comparison to the dry thermometer due to the latent
evaporation.
Determination
of the air humidity using the Assmann aspiration psychrometer
The
significant disadvantage of August psychrometer is its dependence on the air
velocity. The air velocity influences the evaporation intensity and the
device’s wet thermometer cooling.
This
disadvantage has been eliminated in Assmann psychrometer due to the usage of
the ventilator. The ventilator produces the constant air movement at the 4
m/sec speed near thermometers’ reservoirs. As a result data does not depend on
the air velocity either inside or outside of the premises. Furthermore,
thermometers;’ reservoirs of this psychrometer are protected with reflecting
cylinders around psychrometer’s reservoirs from the radiant heat.
The
cambric of Assmann aspiration psychrometer wet thermometer is dampened using
the pipette, the spring of the aspiration devise is set or the psychrometer
with electrical ventilator is plugged in. After these procedures the
psychrometer is hung up onto the support at the determination point. The data
of wet and dry thermometers are taken 8-10 minutes later.
The
absolute air humidity is calculated using the Sprung formula:
,
where:
А – absolute air humidity in
Hg mm;
t – maximum pressure of water
vapour at the wet thermometer temperature (see the table of saturated water
vapours, table 3);
0.5 – constant psychometric
coefficient;
t – temperature of the dry
thermometer;
t1 – temperature of the
wet thermometer;
В – barometric pressure at the determination
moment in Hg mm.
Relative
humidity is determined using the following formula:
,
where:
Р –the value of relative
humidity to be found, %;
А – absolute humidity, Hg mm;
F – maximum humidity at the dry
thermometer temperature, Hg mm
Relative
humidity is determined using the psychrometric tables for aspiration
psychrometers. The value of the relative humidity is found at the intersection
point of the dry and wet thermometer data (see table 5).
Hair
or membrane hygrometers are used for the determination of the relative humidity
of the air. These devices measure the relative humidity directly. The
hygrometer operation is based on the facts, that the degreased hair lengthens,
and the membrane/diaphragm weakens when it’s damp, and vice-versa when they are
dry (see fig. 6.2-c).
Table
5
The
relative humidity standards for residential, public and administrative premises
(abstract from Building Norms and Rules
2.04.05-86)
Note:*
Allowable humidity is 75% for regions with the estimated outdoor air relative
humidity more than 75%.
Standards
are set for people who continuously stay in premises for more than 2 hours.
Humidity
deficit (the difference between the maximum and
absolute air humidity) is determined using the table of saturated water
vapours. The absolute air humidity, calculated using Regnault or Sprung
formulas is subtracted from the value of maximum air humidity according to the
dry psychrometer’s thermometer.
Physiological
humidity deficit (the difference between the
maximum air humidity at 36,5оС body temperature
and absolute air humidity) is determined using the same table of saturated
water vapours (see table 3).
Dew
point (temperature when the absolute air humidity
is maximum) is determined using the same table of saturated water vapours (see
table 3) in reverse direction. The temperature when the absolute air humidity
is equivalent to the maximum, is found using the value of absolute humidity.
The
scheme shows, that the rise of temperature provokes the maximum humidity
increase in geometric progression, the absolute humidity – in arithmetical
progression. When the air temperature rises, the relative humidity is
decreases. As a result the amount of water in the air (absolute humidity) is
essentially lower in cold seasons than in summer, but is closely related to
saturation (maximum humidity). That is why the relative humidity is high in
cold seasons and low in summer usually.
The
daily temperature, the air humidity and the atmospheric pressure variation are
determined using the thermograph, hygrograph and barograph respectively
The
role of earth surface type in appearing of winds
Wind
is air in motion. It is caused by horizontal variations in air pressure. The
greater the difference in air pressure between any two places at the same
altitude, the stronger the wind will be. The wind direction is the direction
from which the wind is blowing. A north wind blows from the north and a south
wind blows from the south. The prevailing wind is the wind direction most often
observed during a given time period. Wind speed is the rate at which the air
moves past a stationary object.
Measuring
of wind speed
Plenty
of instruments can measure wind.
•Wind
vane measures wind direction. Most
wind vanes consist of a long arrow with a tail that moves freely on a vertical shaft.
The arrow points into the wind and gives the wind direction.
•
•Anemometers measure wind speed. Most anemometers
consist of three or more cups that spin horizontally on a vertical post. The
rate at which the cups rotate is related to the speed of the wind. The cup of
anemometer has measuring borders from 1 to 50 m/sec, the wing one – from 0,5 to
15 m/sec.
•Cathathermometer – alcohol thermometer with cylindrical or globular
reservoir and a capillary tube, dilated upwards, can measure air motion speed
from 1,5 to 2 m/sec.
Anemometer -
•A
cup anemometer has metal cups which
rotate in the wind.
•A
swinging-arm anemometer records the
force of the wind against a single ball or plate. With a ventimeter wind blows
into a hole at the bottom of a tube and raises a plate up it.
•A
Dwyer wind meter similarly uses a
ball. You can easily make a simple anemometer.
Usage of "wind rose" in preventive sanitary control for
settlements, industrial enterprises, resting-places building.
The
direction of a wind is determined by that part of horizont from where it blows.
A direction and force of wind is taken into account for need of construction
and planning of cities. As the direction of a wind is constantly changed,
therefore it is necessary to know, what winds dominate in this district. For
this purpose all directions of winds on stretch of season or year are taken
into account. On this data they create the schedule named "rose of
winds". Thus, "rose of winds" represents a graphical image of
recurrence of winds.
Wind
scale
Classification of Wind Speed
Wind
speed can be given according to the Beaufort Scale mainly used to report
weather at sea, "a force 9 gale" for example. On land, various
indicators such as the movement of smoke or
branches, enable the wind speed to be estimated with reasonable
accuracy.
•Force
1: 3 km/h (2 mph) smoke drifts
•Force
2: 9 km/h (5 mph) leaves rustle
•Force
3: 15 km/h (10 mph) flags flutter
•Force
4: 25 km/h (15 mph) small branches move
•Force
5: 35 km/h (21 mph) small trees sway
•Force
6: 45 km/h (28 mph) large branches move
•Force
7: 56 km/h (35 mph) whole trees sway
•Force
8: 68 km/h (43 mph) twigs break
•Force
9: 81 km/h (50 mph) branches break
•Force
10: 94 km/h (59 mph) trees blow down
•Force
11: 110 km/h (69 mph) serious damage
•Force
12: 118 km/h (74 mph) hurricane damage
Wind
Projects and Activities
There are lots of projects related
to wind speed and direction. You can build a lot of the instruments yourself
(look at things to do). Investigate why the wind does what it does!
In
enclosed spaces the running speed of air is determined in meters for one
second. The more air in a location varies, it is purer and health. But to admit
of high speeds of motion of air in a location it is impossible, as flows of
cold air, which one acts in a location, can derivate draughts. Is established,
that the draught can call in the person or offensive feels or sometimes
catarrhal diseases. The feel of a draught is at a running speed of air of
0,5m/sec and above.
•Therefore
at cooling locations it is undesirable to make motion of air with speed of
0,5m/sec and more, specially in a cold season.
•The
motion of air near to temperature and damp it influences heat output by an
organism and, means, on thermo exchange of the person.
•Let's
consider such example. Let's allow, that temperature of air high, or is little
bit lower from temperature of a human body. The relative humidity is high also.
Under such circumstances heat output by a body of the person becomes difficult,
as also temperature of air high. Close up to temperature of a human body. The
stay of the person in such conditions conducts to an overheating.
Atmospheric
pressure
http://www.physicalgeography.net/fundamentals/7d.html
What
is Pressure?
Air
or atmospheric pressure, is the force exerted on the Earth, by the weight of
the air above. That depends on how high the column of air is, so the higher the
surface, the less the pressure. That is why you set your barometer to the
height of your house or school above sea-level to get correct readings. Air
pressure basically refers to the volume of air in a particular environment,
with greater volumes creating higher pressures. On the earth's surface, for
example, it is known as "atmospheric pressure" and refers to the
weight of the earth's atmosphere pressing down on everything. Changes in
pressure can impact the temperature, weather patterns, and cause physiological
problems for people and animals. This pressure can even impact the performance
of a basketball or similarly inflated object.
Atmospheric
Pressure
On the earth, the average air pressure at sea
level is 1.03 kilograms per square centimeter (kg/cm2) or 14.7 pounds per
square inch (psi); this is commonly measured in bars, in which atmospheric
pressure is about 1 bar. This means that hundreds of pounds of pressure are
pressing on everyone from all sides, at all times. Humans and other animals are able to survive
this pressure because their bodies evolved on the surface where it is
natural. If the pressure increases or
decreases, it can result in discomfort or even death.
Changes
in Pressure and Weather
Atmospheric
pressure varies slightly over the earth's surface, and variations in pressure
are responsible for various types of weather.
Low pressure systems are associated with storms, tornadoes, and
hurricanes. Sometimes the air pressure
at sea level can drop as low as 870 millibars, which is about 85% of average
air pressure. This only happens during
the most severe storms. Pressure
variations on the earth's surface cause wind: as high pressure air moves toward
low pressure areas, creating gusts.
Various
Pressures at Different Altitudes
On
the top of Mt. Everest, the tallest mountain on earth, the air pressure is just
about a third of what it is at sea level. Humans at high altitudes often
experience discomfort, such as ear popping, due to differences in their
internal and external pressures. At 16
kilometers (km) or almost 10 miles above the surface, slightly higher than the
cruising altitude of a typical jet liner, pressure is only 1/10th what it is at
sea level. Because low air pressure can
be very unpleasant for humans, due to low oxygen content, all areas of aircraft
that contain passengers are artificially pressurized. In the event of a rupture
in an airplane's fuselage, unsecured items may be "sucked" out of the
craft as the high pressure air within it rushes out into the low pressure
environment outside.
Higher
Altitudes and Outer Space
At
31 km or about 19 miles above the
earth's surface, in the stratosphere, the air pressure is only 1/100th what it
is at sea level. From this level on, the
atmosphere quickly deteriorates into nothingness. Above 100 km or just over 62 miles above the
surface, the international definition for outer space, the pressure approaches
zero and nearly becomes a vacuum. Humans cannot exist unprotected in such a
low-pressure environment.
Why
is it Important?
Different
pressure regimes have different types of weather associated with them.
Barometer
readings are plotted on a pressure chart. Points on a map that have the same
air pressure are connected by lines known as isobars. By studying the patterns
shown by isobars, forecasters can make predictions about how the weather will
develop. We can identify "troughs" of low pressure and
"ridges" of high pressure.
Barometer
http://www.stuffintheair.com/barometermakes.html
Types
of barometers
Mercury
siphon barometer
consists of long vertical tube.Instrument contains mercury. We get the result
after summation of hailing mercury tube in long and short knee.
Mercury-cupping
barometer consists of vertical glass tube which has mercury
solder in upper part and open in lower part. Lower part is put into cup with
mercury.
Metal
barometer aneroid. Main
part of this barometer is metal reservoir with cavity. When pressure changes,
change volume and forms of reservoir with mercury.
http://www.bom.gov.au/info/aneroid/aneroid
Barograph.
Point of instruments connects with metallic aneroid.
The recording barometer may be day and week periodical. To establish of the
periodicals it is necessary to open the device’s case, to take down from the
drum’s axis for the tape and on it’s lower part to see on what period well
calculated clock mechanism. 747 Millimeter of a mercury column x 4/3 = 963
mB.This quantity we put on the tape instead of the beginning record time.
There
is a scheme of an estimation of air behind damp: air name dry, when a water
pair in this there are less than 55 %, slightly dry – at 56 up to 70 %, by
slightly wet - from 71 up to 85 %, hardly wet - have more 86 % and saturated -
100 %.
The
business in that in miscellaneous terrains prevalence a direction of winds
happens miscellaneous. What the dominating direction of winds means? This is a
direction, which one often repeats during one year or season.
On
meteorological stations permanently registry can be defined a cosines speed of
their motion and directions a direction of winds on 4-8 or 16 rhombs. E -
Eastern wind, that is wind, that winds from east. W- Western wind; N - Northern
wind; S – Southern, NE - Northern – Eastern. At a sanitarian estimation of the projects of settlements the availability
on the schedule of a wind rose enables fast and simplly to orient and to
evaluate a regularity of accommodation miscellaneous regions, objects. For
example, the regularity of mutual accommodation of industrial firm, which one
will flare air of habitation point.
The formation of gas bubbles in the
organism during ascent is called decompression sickness, known also as “the
bends”.
Symptoms They
occur 5 minutes to 1 hour after the ascent, sometimes after 2-4 hours. Symptoms
range cough, itching, reddened skin or pains in the joints to serious
respiratory, cardiac and mental damage (such as rapid pulse and heart beat,
shortness of breath, pains in the chest and stomach, paralysis of limbs)
Treatment The
only remedy to do away with decompression sickness is the chamber for
recompression. The diver is exposed to the same pressure (at which he was
before the beginning of bubbles’ formation), necessary to dissolve the bubbles.
Afterwards, the pressure decreases on stages to avoid decompression sickness.
HOW
DOES AIR PRESSURE AFFECT THE BODY?
Air
pressure is the force that is exerted on you by air molecules; the weight of
tiny air particles. Atmospheric pressure is a measure of the force exerted by
the atmosphere, so therefore at any point on the earth’s surface, there is a
quantity of air sitting above your body. If that quantity of air is greater,
there will be more pressure on the body; and if it is less, there will be less
pressure on the body. This is traditionally measured in pounds per square inch
(PSI). 1 PSI is the force of one pound applied to an area of one square inch.
At
high altitudes the quantity of air is less, and the density of air is also
less. As such, there is less air pressure and as a result, less oxygen in a
given volume of air. To demonstrate this, If a person dives below the surface
of water in scuba diving, their body has to contend with both the air exerting
pressure on the surface of the water, and the water above that exerting further
pressure, hence, the deeper you dive, the more pressure there is.
At
sea level, we say atmospheric pressure is 1 atmosphere (this is equal to 14.7
psi). This arbitrary measurement provides a reference point from which we can
determine air pressure at varying altitudes or depths.
For
every 10 metres deep which you go in water, the pressure increases by 1
atmosphere. For example -at 10 metres it is 2 atmospheres; at 40 metres it is 5
atmospheres).
HOW
DOES THE HUMAN ORGANISM LOSE A HEAT?
Major
part of heat loses through the skin and mucous, other part goes on heating of
food, water and breathes air. Through the skin loses main heat mass: for after
one authors - 85-90%, after other - even 95%, so, only 4-6% loses on heating of
food, breathe air and waters.
http://www.expeditionsamoyeds.org/Hypothermia.html
Because
of that interestingly will learn how the heat is lost by skin. Appear, that
skin loses a heat by three ways:
•by
radiation,
•taking and
•on
evaporation of sweat moisture.
For
data of Rubner, we can say, that man attached to light work in room conditions
•loses
by radiation about 40%,
•taking
- about 30% and
•by
evaporation - about 20% of heat.
These
ciphers are directed for orientation, and really they consider vacillate
dependency on conditions.
What
is the heat losing way by radiation?
From
physics we know, that any more heated body radiates more heat, than less
heated. So, even not colliding with it, it gives to it its heat, while the
temperatures of both bodies will not complete with each other.
•Man
in room conditions is usually circled by objects with more low temperature,
than his body, that is why takes place heat losing by radiation.
•Also
heat is lost by installation. In this case a heat is lost by two ways - conduction and convection.
•Conduction is a heat transition on the strength of
contiguity of objects, and also air parts from more heated to less heated. Convection is a heat transmission on the strength of
mediators - air, steam, liquid, the fractions of which, heating attached to
contact with more warm body, bear off heat and return it attached to contiguity
with more cold objects. On the strength of temperature difference in
intermediate environment, for example, in air, the convectional streams are
generated.
•The
third way of heat losing is evaporation
of moisture.
A
human skin is always covered by sweat, water of which evaporates. For this
process it is necessary expenditure of warm /secretive evaporation temperature
/.
http://ppo.tamuk.edu/ehs/Heat_Stress/heatstress.htm
Microclimate –
it is meteorological conditions in work zone,
which characterized by complexes of factors that act on organism of peoples it
is temperature, humidity and rate movement of air, and also radiation
temperature and warm radiation. Temperature of air is favorable factors which
influence on heat exchange. Radioactive temperature – it is the temperature
that surround people of superficiality or intensive sun or another radiation.
Microclimate
is a thermal status of the limited space. It results from combined action of
air temperature, radiation heat, air humidity and air movement velocity.
Microclimate defines heat state of an organism. Microclimate is influenced by
latitude, topography, human activities and vegetation as well as other factors.
Sometimes they mean microclimate as variations of the climate within a given
area, usually influenced by hills, hollows, structures or proximity to bodies
of water. The warmth and humidity of the air in close proximity to a plant or
heat/moisture source may differ significantly from the general climate of the
premise.
Air
treatment/air cooling differs from ventilation because it reduces the
temperature of the air by removing heat (and sometimes humidity) from the air.
Air conditioning is a method of air cooling, but it is expensive to install and
operate. An alternative to air conditioning is the use of chillers to circulate
cool water through heat exchangers over which air from the ventilation system
is then passed; chillers are more efficient in cooler climates or in dry
climates where evaporative cooling can be used.
Local
air cooling can be effective in reducing air temperature in specific areas. Two
methods have been used successfully in industrial settings. One type, cool
rooms, can be used to enclose a specific workplace or to offer a recovery area
near hot jobs. The second type is a portable blower with built-in air chiller.
The main advantage of a blower, aside from portability, is minimal set-up time.
Another
way to reduce heat stress is to increase the air flow or convection using fans,
etc. in the work area (as long as the air temperature is less than the worker's
skin temperature). Changes in air speed can help workers stay cooler by
increasing both the convective heat exchange (the exchange between the skin
surface and the surrounding air) and the rate of evaporation. Because this
method does not actually cool the air, any increases in air speed must impact
the worker directly to be effective.
If
the dry bulb temperature is higher than 35°C (95°F), the hot air passing over
the skin can actually make the worker hotter. When the temperature is more than
35°C and the air is dry, evaporative cooling may be improved by air movement,
although this improvement will be offset by the convective heat.
When
the temperature exceeds 35°C and the relative humidity is 100%, air movement
will make the worker hotter. Increases in air speed have no effect on the body
temperature of workers wearing vapor-barrier clothing. Heat conduction methods
include insulating the hot surface that generates the heat and changing the
surface itself. Simple engineering controls, such as shields, can be used to
reduce radiant heat, i.e. heat coming from hot surfaces within the worker's
line of sight. Surfaces that exceed 35°C (95°F) are sources of infrared
radiation that can add to the worker's heat load. Flat black surfaces absorb
heat more than smooth, polished ones.
Having
cooler surfaces surrounding the worker assists in cooling because the worker's
body radiates heat toward them. With some sources of radiation, such as heating
pipes, it is possible to use both insulation and surface modifications to
achieve a substantial reduction in radiant heat.
Instead
of reducing radiation from the source, shielding can be used to interrupt the
path between the source and the worker. Polished surfaces make the best
barriers, although special glass or metal mesh surfaces can be used if
visibility is a problem.
Shields
should be located so that they do not interfere with air flow, unless they are
also being used to reduce convective heating. The reflective surface of the
shield should be kept clean to maintain its effectiveness.
HVAC
(heating-ventilation-air conditioning) system defines indoor microclimate.
A
microclimate maintenance system (general HVAC system) created in several rooms
gives a possibility to use an economic decision, the idea of which consists in
use of one outdoor unit and several indoor units (from two to four). It is
explained by the fact that in adjacent room’s air-conditioners have to carry
out similar functions of cooling or heating.
This
makes it possible to use one outdoor unit for work with indoor units which
carry out cooling, for example. As a result such a system has lower operating
costs and lower power consumption and at the same time allows you to carry out
air-conditioning in one or several rooms, where indoor units are installed.
HEAT
BALANCE
Fundamentals
of heat transfer Humans are homeothermic, which means they must maintain body
temperature within a narrow range in varying environmental conditions. The
normal deep body temperature (core body temperature) at rest is between 36-37.5
oC, although extremes in excess of 40 oC have been recorded in athletes and
workers exposed to very severe environmental conditions. These temperatures are
at the upper limit of human physiological tolerance, however they illustrate
that people do get exposed to such conditions during their work practice. The
variation of resting core body temperatures also demonstrates the individual
diversity that may exist in a working population. This variation means that
people may have different tolerances to working in the heat. Some people cannot
tolerate mild increases in core body temperature whereas others, as
illustrated, can continue to work at much higher temperatures. The factors that
may account for this variation among workers are still, however, poorly
understood.
Thermal
homeostasis is maintained by achieving a balance between the various avenues of
heat gain and heat loss from the body. There are two recognised sources of heat
load;
a)
Environmental, which may be positive or negative, that is, there may be a heat
gain or a heat loss from the body.
b)
Metabolic, which is generated by muscular activity.
ENVIRONMENTAL
FACTORS AFFECTING THERMOREGULATION
The
principal methods of heat exchange between the body and the external
environment
are: convection, conduction, radiation and evaporation.
Convection
The
rate of convective exchange between the skin of a person and the ambient air in
close proximity to the skin, is dictated by the difference in temperature between
the air and the skin temperature together with the rate of air movement over
the skin.
When
the air temperature is greater than the skin temperature, there will be a gain
in body heat from the surrounding air, conversely when the skin is warmer than
the air temperature there will be a loss of heat from the body. Because warm
air rises (less dense than cool air) the warm air will rise from the body and
cool air will come in to take its place. This process is then repeated. The
process is called convection.
Radiation
The
surface of the human body constantly emits heat in the form of electromagnetic
waves. Simultaneously, all other dense objects are radiating heat. The rate of
emission is determined by the absolute temperature of the radiating surface.
Thus if the surface of the body is warmer than the average of the various
surfaces in the environment, net heat is lost, the rate being directly
dependent on the temperature difference. This form of heat transfer does not
require molecular contact with the warmer object. The sun is a powerful
radiator, and exposure to it greatly decreases heat loss by radiation. When the
temperature of the objects in the environment exceeds skin temperature, radiant
heat energy is absorbed from the environment. Under these conditions the only
avenue for heat loss is by evaporative cooling.
Conduction
The
difference between heat loss by conduction and radiation is that with
conduction the body must be in contact with the object. In such circumstances
the heat moves down its thermal gradient from the warmer to the cooler object,
the heat energy being transferred from molecule to molecule. The warmer
molecule slows down after it has lost some of its heat and the cooler molecules
move faster having gained heat. The temperature transfer continues until
eventually the temperature of the two objects equalises. The rate of the heat
transfer through conduction depends on the difference in temperature between
the two objects and the thermal conductivity of the two objects.
Evaporation
When
water evaporates from the surface of the skin, the heat required to transform
it from a liquid to a gas is dissipated from the skin, this acts to cool the
body. Evaporative heat loss occurs from the respiratory tract lining as well as
from the skin. There is a constant gradual loss of water from the skin that is
not related to sweat glands. The skin is not fully waterproof and so some water
is lost out through pores in skin, and lost by evaporation. This loss is not
subject to physiological control and is termed insensible perspiration.
Sweating is an active process requiring energy and controlled by the
sympathetic nervous system. The rate at which this process proceeds can be
controlled and therefore the amount of heat loss can be controlled.
Radiation
and convection are insufficient to prevent warming up of the body during heavy
manual work or at high surrounding temperatures. Under these circumstances heat
loss is aided by evaporation of water. At environmental temperatures above
about 36 oC, heat is lost exclusively by evaporation. At higher temperatures
heat is taken up by the body from the environment by radiation, conduction and
convection.
Sweating
then becomes profuse in order to maintain the balance between heat uptake and
heat loss by evaporation. In order to be effective, sweat must be evaporated
from the skin. If sweat merely drips from the surface of the skin or is wiped
away, no heat will be lost.
METHODS OF DETERMINATION OF
THE NATURAL LIGHTING INDICES IN DIFFERENT PREMISES
Descriptive
data:
1.
External
factors that influence natural lighting in different premises:
- the
territory latitude and its climate (number of sunny and cloudy days);
- season of
the year and time of the day, when the premises are being used, existence of
objects producing shadow (buildings, trees, hills, mountains).
2. Internal factors:
- name and
function of premises;
- window
orientation, floor;
- type of
natural lighting, (light aperture location), (one-side, two-side, upper and
combined);
- number of
windows, their construction (one-framed, two-framed, combined);
- clarity and
quality of glass, existence of objects producing shade (flowers and curtains);
- the
window-sill height, distance from the window top edge to the ceiling;
- brightness
(reflection ability) of the ceiling, walls, equipment and furniture
The above
mentioned factors also influence the premises insolation regimen (the duration
of exposure to the direct solar light). It can also be influenced by the
windows’ orientation. (table 1).
Table 1
Types of
premises isolation regimen
According to
the hygienic norms the duration of insolation in residential areas, classrooms
and other premises of similar functions must be not less than 3 hours.
The
assessment of natural lighting in different premises using the geometric method:
1.
The lighting
coefficient determination (the ratio of the glazed part area to the floor area,
expressed in common fraction);
- the total
area of the glazed window part is to be measured (S1), m2;
- the area of
the floor is to be measured (S2), m2;
- the
lighting coefficient is to be measured (LC=S1:S2=1:n) (n is calculated as S2 divided on S1
and approximated to the integer).
The received
result is assessed according to the hygienic norms (table 2).
Table 2
The natural
lighting norms for different premises
2. Determination
of the angle of incidence a (the ABC
angle at the furthest workplace from the window is formed by the horizontal
line (or plane) AB from the workplace to the lower window edge (window-sill)
and the line (plane) AC from the workplace to the upper window edge) (fig.
4.1).
Fig. 4.1.
Diagram for determination of the angle of incidence and the angle of aperture
The aperture
angle calculation:
tg a=BC/AB (see table of tangents), a - the angle of incidence;
tg b=BD/AB (see table of tangents), b - the angle of shading;
Conventional
marks:
BC- the
height from the upper window edge to the work plane level, m;
AB- the
distance from the window to the furthest work place, m;
BD- the
distance from the projection of the shadowing object’s top onto the window
glass to the level of the worktop, m.
As this angle
together with the window glass line form the right triangle, it must be
determined by tangent – the ratio of the window height above the workplace
level (BC) (opposite cathetus of the triangle) to the distance from the window
to the workplace (AB) (adjacent cathetus of the triangle). The angle of
incidence a is found by the tangent value using the table.
The indoor and outdoor lighting is
measured by luxmeter (see the instruction, appendix 2 and fig. 4.2).
Fig. 4.2. Luxmeter U-116 (Ю-166)
(1 – measuring device (galvanometer); 2 – light receiver (selenium
photo-cell); 3 – changing light filters)
The part of
the sky can be hidden behind the tall buildings and trees in the cities or by
mountains in highlands. That’s why the curves of the regional lighting climate
are used in practice (fig. 4.3).
The curves, shown on the fig.4.3, include months, hours
and the level of cloudiness. The ordinate axis has lighting indicators, marked
in thousands of lux.
The natural lighting of factory
sections may be side (one-side, double-side), upper (light apertures in the
ceilings) and combined.
According to the Building Norms and Rules (BNandR)-4-79, the daylight factor (DF) is calculated:
- in case of one-sided lighting – at the distance of 1 m from the
opposite wall;
- in case of double-sided
lighting - in the middle of the section;
- in case of the combined
lighting, the average of the several lighting measurings, performed using the
“envelope” method is calculated (table 4).
TRAINING
INSTRUCTION
on lighting determination using the
luxmeter
The front panel of the luxmeter also contains the
switching buttons, and the scheme, that explains the effect of each button when
using different light filters. There are two different scales at the device’s
panel: the 0 – 100 scale, and the 0-30 scale. Each of them has the starting
point of its measuring range marked: on the 0-100 scale that is 20, and on the
0-30 scale – 5. Also there is the screw-adjusted regulator for setting the
device to zero.
The selenium photo-cell connected to the device with the
plug is hidden in the plastic case. The spherical light filter, made of white
light dispersing plastic and the opaque ring, is used with the photo-cell for
more exact measuring. This filter is used simultaneously with one of the three
changing filters. These changing filters have different attenuations (10, 100
and 1 000), and they extend the measuring range.
The process of the measuring consists of the following:
1)
The device is
set to 0;
2)
By trying the
different combinations of the pressed buttons and changing filters, the appropriate
scale for the present light is found. When the button, next to which the
ranges, divisible by 3 are written, the 0-30 scale is used. When the button
with the ranges, divisible by 10 is pressed – the 0-100 scale is used;
3)
The measuring
result in scale marks is then multiplied by the attenuation value of the filter
used.
The U-116 (Ю-116) or U-117 (Ю-117) luxmeter is graded for measuring the light, produced
by the incandescent lamps. The correcting coefficients are used for the other
types of light. For the natural light its value is 0.8, for the fluorescent
daylight lamps – 0.9, and for the white lamps – 1.1.
The general assessment of the natural lighting in
different premises is made by comparing the results of all measurements with
the hygienic norms. The accuracy of visual work is the base for these norms. It
includes the sizes of the visual objects, their contrast against the background
etc.
For the convenience the results of measurements and the
hygienic norms are written into the table:
To draw the final conclusion about the natural lighting of
different premises it is necessary to compare the assessment of each result
with the norm.
Physical characteristics of artificial illumination
1. The artificial illumination (same as natural) is characterized
by:
- light intensity
(I)- the light source capacity, measured in candles
(Cd). It’s a light intensity, that generates the monochrome radiation of the
540∙1012 Hz
frequency in certain direction, with radiant intensity in that direction of
1/683Wt/steradian;
- light flow
(luminous flux) (F) - the density of light, measured in lumens (lm) - light flow, radiated by the
individual source with intensity of 1 cd in the solid angle of 1 steradian. The
solid (spatial) angle is the cone, which, if its top is considered to be in the
center of the sphere, cuts the surface, equaling to the squared radius of that
sphere from it;
- illuminance
(E)- the amount of light falling on a surface (surface density of the light
flow) , where S is the illuminated surface area, m2. The
illuminance is measured in luxes. 1
lux is the illuminance of the 1 m2 surface,
illuminated by the light flow of 1 lumen;
- brightness (B)
–light intensity, at which the light is radiated or reflected from the surface
in certain direction. , where is the angle
between the light direction and the perpendicular to the surface.
The unit of brightness is cd/m2 - the brightness of the surface with
the area of 1m2, radiating or reflecting the light with the
intensity of 1cd;
- reflection
coefficient (β) - the ratio of the reflected light flow (Fref)
to the light flow received by the surface (Frec). It is calculated
using the following formula .
The β value is 0.9 for fresh snow, 0.7 – for white
paper and 0.35 – for untanned skin.
- optical transmission coefficient (τ) is the
light flow, which goes through the (Fthrough.) medium, divided by
the light flow, which falls on that medium .
This coefficient allows assessing the quality and the
cleanness of the window glass and the glass parts of different lighting
fixtures.
- luminosity (M)
– surface density of the light flow, expressed in lm, which is radiated from
the 1m2 surface (lm/m2).
2.
Human vision
- visual acuity (the
recognition ability) is the ability of the visual analyzer to recognize the
smallest elements of the object. It’s determined by the smallest angle, under
which the two adjacent spots are recognized as separate. The visual acuity is
conventionally considered to equal to one angular minute. The visual acuity
grows proportionally to the illuminance until it reaches 130-150 lux. When the
illuminance is above that point, the visual acuity growth slows down.
- contrast
sensitivity is the ability of the visual analyzer to perceive the minimum
difference between the brightness of the object and the background. It reaches
its highest level when the illuminance is 1 000-2 500 luxes;
- visual perception
speed is the time, required to recognize the details of the object. This
speed grows until the illuminance reaches 150 luxes. After that point, the
growth slows down unproportionally to the illuminance growth;
- visibility is
the integral function of the visual analyzer, which is the combination of its
main functions – visual acuity, contrast sensitivity, visual perception speed;
- clear vision
stability is the time, during which the object can be clearly seen to the total
time of the object examination. Physiologically this function of the visual
analyzer based on the destruction of the visual purple (rhodopsin) under the
influence of the light and formation of the protective black pigment on those
parts of the retina, where the picture is the brightest. This function reaches
its optimal value at the illuminance of 600-1 000 luxes. Its reduction is
the evidence of the visual analyzer fatigue;
- color recognition
function. White, black, grey – achromatic colours are only characterized by
brightness and light flow intensity. Chromatic colours (monochromatic) are
characterized by brightness and chromaticity. Vision is the most sensitive to
the yellow and green part of the visual spectrum and the least sensitive to the
violet light. During the twilight or under the artificial illumination
(especially with incandescent lamps) the visual analyzer’s colour recognition
reduces and may distort;
- adaptation is visual analyzer’s ability to reduce its sensitivity during the change
from low to high illumination (light adaptation), (achieved very quickly, (in
2-3 minutes) and is caused by the visual purple conversion into the protective
black pigment in the retina), and to increase it again when the illumination
changes from high to low level (adaptation to darkness), which takes much
longer – up to 40-60 minutes and is caused by the restoration of the visual
purple in the retina;
- accommodation
is the ability of the eye to regulate the visual acuity depending on the
distance to the examined object and illumination due to the changes in the
light refraction in the optic system of the eye, which is mostly caused by the
chrystalline lens curvature change. The curvature will increase when the
illumination is less than 100-75 luxes. So, in such circumstances the object
must be closer to the eye for the proper recognition;
The insufficient illumination leads to the overstrain of
accommodation system, overstrain of the visual analyzer, and for children and
adolescents (their eye has not yet formed completely) it may cause the myopia
(short-sightedness) especially if they have the congenital disposition;
- critical flicker
frequency is determined by the time, during which the afterimage remains in
the visual analyzer: the image of an object, which has disappeared from the
visual field still remains visible for some time depending on the object
brightness. This visual function is based on the same processes of visual
purple destruction and restoration. The cinema, one of the most important human
inventions, is based on it. The frequent change of the frames and the almost
similar objects (25 frames per second), and the darkening of the screen
provides dynamic and continuous picture.
The sources of artificial illumination may be electric and
non-electric. Non-electric sources are kerosene, carbide lamps, candles and gas
lamps. Their use nowadays is mostly limited to the field conditions and
emergency situations. The electric sources of artificial illumination may be
arc lamps (in searchlights, floodlights, spotlights etc), incandescent lamps,
gas-discharge lamps and luminescent lamps.
The disadvantage of incandescent lamps is the spectrum
parallax in the yellow-red direction, the distortion of the color perception,
the dazzling (blinding) effect of direct rays.
The luminescent lamps have the spectrum, almost similar to
the day light with modifications, depending on the luminophor, that covers the
internal surface of the glass tube and transforms the ultraviolet luminescence
of mercury vapour in the tube into the visible light. There are the daylight
lamps (DL), white light lamps (WL), warm white light lamps (WWL) etc.
The disadvantage of luminescent lamps is the stroboscopic
effect - the flickering of moving objects.
One of the disadvantages of both the direct sunlight and
bright sources of artificial illumination is their ability to cause the
dazzling effect. We protect ourselves from the bright sunlight using the
curtains and jalousies, dark-toned windows, the sun glasses.
The lighting fixtures (also used for the aesthetic
purpose), are used for protection from the dazzling effect of artificial light
sources.
The lighting fixtures are divided onto 5 types according
to light flow formation (see fig. 5.1):
- direct light type, directing the whole light flow into
one hemisphere (the table lamp with the opaque lamp-shade, spotlights, floodlights,
and other fixtures used in photo and movie shooting);
- evenly-diffusing the light (dim or light-white sphere);
- reflected light (when the lamp with the opaque
lamp-shade directs the light flow towards the upper hemisphere);
- directed-diffused light type, when the main light flow
is directed towards the lower hemisphere through the aperture in the lamp-shade
and the other part is diffused to the upper hemisphere through the lamp-shade
made of plastic, dim or light-white glass;
- reflected-diffused light type, when the main light flow
is directed towards the upper hemisphere and is reflected from the ceiling but
a part of it is diffused to the lower hemisphere through the lamp-shade with
dim or light-white glass.
The allowable values of dazzling at the workplace are:
-20 cd/m2 for types 1 and 2 of the visual work;
-40 cd/m2 for the types 3-5 of the visual work;
- 60 cd/m2 for the types 6 and 7 of the visual
work.
Fig.5.1. Types of lighting fixtures
(1 - direct light type, 2 - directed-diffused light type;
3, 4 - evenly-diffused light type;
5 - reflected-diffused light type)
Appendix 2
The scheme of the artificial illumination assessment in
different premises
Descriptive data:
-
name and
function of premises;
-
system of illumination
(local, general and combined);
-
number of
lights, their types (incandescent, luminescent and other lamps);
-
their
capacity, Wt;
-
type of
lighting fixture, light flow direction and formation (direct, evenly-diffused,
directed-diffused, reflected, diffused-reflected);
-
height of the
lamps above the floor and the work plane;
- illuminated area;
- reflection ability
(brightness) of ceiling, walls, windows, floor, furniture and other surfaces.
Illumination determination using the ‘Watt’ calculation
method:
a)
the area of
the premises is determined, S, m2;
b)
the total
capacity of all the lamps, Wt, is determined;
c)
the specific
capacity, Wt/ m2, is
calculated;
d)
the
illuminance at the specific capacity of 10 Wt/m2 can be found from
the table 1 of minimum horizontal illuminance values;
e)
for the
incandescent lamps the illuminance is calculated according to the following
formula:
where, P – is
a specific capacity, Wt/m2;
Etab -
illuminance at 10 Wt/m2, (from table 1);
K – which equals
to 1.3, is the reserve coefficient for residential and public premises.
Table 1
The (Etab) minimum horizontal illuminance
values at the specific capacity (P) of 10 Wt/m2
This formula may be applied for the illumination
calculation if all the lamps have the same capacity. The calculations are done
separately if there are lamps with different capacity. Their results are added
up. The received illumination value by the “Watt” method is compared to the
normative values (table 2).
Table 2
Standards of
the general artificial illumination (BNaR II-69-78 and BNaR II-4-79)
For the luminescent lamps with 10 Wt/m2 specific
capacity the minimum horizontal illumination is 100 luxes. The minimum
horizontal illumination for other specific capacities is calculated
proportionally.
For the industrial areas, according to BNandR II-4-79, all
activities are divided into seven types of work, based on the linear dimensions
of the smallest object, worked with at the distance of 0.5 m from the eye. The
first 5 types are divided into 4 sub-types (a, b, c, d), based on the contrast
between the examined object and the background, and the background luminosity.
For example, during the especially accurate work (type 1, the object size is
less than 0.1 mm), the illumination at the workplace must be 1 500 luxes
if the contrast with the background is low; 1 000 luxes if the contrast is
medium and 400 luxes if the contrast is high. When the work is of low accuracy
(type 4, object size is 1.0-10 mm ), the illumination must be 150, 100, 75
luxes respectively.
The above mentioned method is not fully precise as it
doesn’t take the illumination in each point, lamp location and some other
factors into the account, but is often used for the classes, wards and other
areas illumination assessment.
To determine the illumination at the definite workplace,
the lamp specific capacity (P) must be multiplied by the coefficient (e), which
shows the amount of luxes, given by the 1 Wt/m2 specific capacity: E
= P×e. This coefficient for the premises of 50 m2 area and the
lamp capacities of less than 110 Wt is 2, 110 Wt and more – 2.5 (see table 3)
and 12.5 for the luminescent lamps.
Table 3
The values of the coefficient e
Illuminance determination using the luxmeter.
The determination of horizontal illuminance at the workplace
is done with the help of luxmeter (see topic 4, appendix 2). The 0.9 correction
coefficient is used for the luminescent lamps of day illumination (LD); 1.1 -
for the white lamps; 1.2 - for the mercury-discharge lamps, because the device
has initially been intended for measuring of the illuminance, produced by
incandescent lamps.
If the determination is done in the morning or in the
afternoon, it’s necessary to determine the illuminance, produced by the mixed illumination
(both natural and artificial). After that the determination is done when the
artificial illumination is switched off. The difference between the received
data is the value of illuminance, produced by the artificial illumination.
The illumination evenness is determined by the “Envelope
method,” which means that illuminance is measured at 5 different points of the
premises and evaluated by calculation of illuminance variety coefficient
(minimum illuminance divided by the maximum illuminance at two different
points, which are 0.75 m from each other, when the evenness is determined at
the workplace, or 5 m from each other, if the evenness is determined in the
whole room).
The calculation of the workplane brightness is made using
to the formula:
where, B - is
brightness, cd/m2;
E - illumination, lux;
C - coefficient of surface reflection
(0.7 - white;
0.5 - light-beige; 0.4 -brown; 0.1 - black).
The allowable brightness of general illumination lamps for
residential and public premises is given in the table 4.
Table 4
The allowable brightness values of general illumination
lamps for residential and public premises
The height of the lamps above the floor and the working
place, and the location of general light lamps in the horizontal plane of premises
is of the great importance for creating the sufficient and even illumination,
and for the protection from dazzling. When the illumination is general or
combined, the lamps of general light are located evenly in the horizontal plane
of the ceiling (when it is necessity to create sufficient illuminance in every
point of premises), or they are locally concentrated (to create the high
illuminance in certain parts of the room). The lamp height above the floor must
be not lower, than values, given in the table 5 to minimize the dazzling effect
of the lamps.
The best illumination conditions are created when the
optimal ratio between the distance between the lamps in horizontal plane (L), and
their height above the work-plane (H) is used. These ratios have been found as
a result of the determination of the light distribution curves of different
lamps. The optimal values are shown in table 6.
Table 5
The lowest height of the lamps above the floor (m)
Table 6
The optimal ratios between the distance between the lamps
and their height above the work-plane (L/H)
The sources of artificial
lighting.
There are two main sources of artificial
lighting: incandescent bulbs and luminescent lamp. A bulb is very convenient
source of light. Its deficiency is a very small light returning: on 1 Vat of
expended electric energy one can receive 10-20 lm. The spectrum of its
radiation differs from the spectrum of white daylight. It has less quantity of
blue and violet radiation and more red and yellow one. That’s one taking into
consideration psycho-physiological side this radiation is pleasant and warm.
Luminescent lamp consists from glass tube. The internal
surface of this glass is covered by luminoforum. The tube is full of mercury
steam. At the ends it has electrodes. When the lump is switched in the electric
net on, the electric current creates between the electrodes. It generates
ultraviolet radiation. Under ultraviolet radiation influence luminofor starts
to shine. Thus choosing different kinds of luminofor one can made luminiscent
lamps with different spectrum of visible radiation: lamps of day light, white
light, warm-white light. The spectrum of day light lamp radiation is very
clothing by spectrum of natural lighting of lodging, situated on the north.
This light helps to get tired less, even if we look at very small subject. To
deficiency of lamp one can attribute blue color at surroundings: skin… and so
on.
Lighting appliance of bulbs.
There are lighting appliance of
direct light, reflected light, half-reflected light, and diffused light. The
lighting appliance of direct light directs over 90% of lamp light to the
lighting place, providing its high lighting. But at the same time there is a
great difference between the lighting and sun lighting places of lodging. Harsh
shadows are created sometimes it can blind there person. Usually this kind of
lighting appliance is used for lighting of auxiliary lodging and sanitary
lodgings. The appliance of reflected light is characterised by the fact, that
rays from lamp are directed to the ceiling and upper part to the walls. They
are repulsed, and evenly, without shadows, are divided in lodging. Their light
is soft and diffused. This kind of lighting appliance creates lighting, which
exactly corresponds to hygienic norms. But it is not economic one. Because in
this case 50% of light is lost. That’s for lighting of settlements, classrooms,
wards more economic lighting appliance is used – appliance of diffused light.
In this case a part of rays shine the lodging after coming through milk or mat
glass, and part of rays shine the lodging after repulsing from ceiling and
walls. Such lighting appliance creates satisfactory conditions of lighting,
does not blind and doesn’t create harsh shadows.
Deficiencies of luminiscent
lamps (compared with bulbs).
One of the deficiencies of
luminiscent lamp is that the skin of people in this light looks very pale or
grey. That’s why there lamps are not used in schools, wards and others lodging
like these. Becides there are another deficiency. If lighting in case of using
luminiscent lamps is power than 750-150 Lk, one can see “twilight effect”. That
means lighting is insufficiently even to look at big object. That’s why while
using luminiscent lamps, lighting should be not less than 75-150 Lk. Besides
while looking at moving or rotating object in luminiscent lighting sometimes
“stroboscope effect” can occur. That means creating of numerous contours of
objects. When dossals are out of order luminiscent lamps radiate pulse light or
create noise.
The spectrum of worm-white lamps is
rich on yellow and rose rays. This can make the colour of face more pleasant.
But at the same time these lamps decrease eye capacity for work. These lamps
are used for lighting of railway station, hall, and cinemas, metro stations.
Advantages of luminiscent lamps compared with bulbs.
The bulb cannot be
used when one need to differentiate colours well. In this case one should use luminiscent
lamp of daylight. Lamps of white light have spectrum rich on yellow rays.
That’s why while using true lamps great capacity for eye work is presented, and
skin colour looks great. That’s why lamps of white light are used in schools,
lecture rooms, settlements, and wards of hospitals. Spectrum of lamps of
warm-white light is rich on yellow and rose radiation. This fact makes less
capacity for eye work, but makes the skin colour very pleasant. Variety of
spectrum is one of the hygienic advantages of these lamps light returning of
luminiscent lamps is in 3-4 times higher than light returning of bulbs. That’s
why they are more economic. During numerous comparative investigations with
bulbs on industrial plants, in schools, hospitals, lecture rooms objective
induces, which characterise the nervous system state, weariness of eye,
capacity for work almost in all cases prove hygienic advantage of luminiscent
lamps. But for their wide usage we need professional help. It is necessary to
choose the lamp correctly, according to its spectrum, taking into consideration
purpose of the place.
Methods of definition of artificial lighting.
Artificial lighting can be defined by means of calculate
methods, for example the methods of middle horizontal lighting. The principle
of the methods is the following: if we use 10 Vat of electro energy stress on
each square meter of floor, we receive the middle horizontal lighting. It
depends on the force of used lamps. While the same expenditure of energy on
square unit lighting can be different. It can be explained by different
lighting returning of lamps of different force. Using data about lighting while
expending energy (10 Wt/m2 ) and taking into consideration that
received lighting depends directly on expended energy, one can find artificial
lighting. For this we use the quantity of lamps with certain power and quantity
of chalendeliers with certain power, which it is necessary for certain
lighting. For example, it is necessary to find middle horizontal lighting in
classroom. Its floor’s square is 50 m2. . We also know that 6
chalendeliers are used. The force of each lamp is 200 Wt. The voltage in net is
120 V. Taking into concideration all the conditions, general electro energy
force, which is used to shine the classroom is 200 x 6 =1200 Wt. On 1 m2
of floor we have 1200:50 = 24 Wt/m2. For lamps 200 Vat in case of energy
expenditure 10 Vat/m2 lighting E will be 35,5 Lk. The lighting will
be higher in so many times, as the energy expenditure is higher then common on
square unit:
10/24=35,5/E; E = 85,2 Lk.
Proper power
(Wt/м2)
of general
illumination
|
Height of
hanging of lamps, м
|
Square of the apartment
м2
|
Level of illumination, lux
|
|
30
|
50
|
75
|
100
|
150
|
200
|
300
|
400
|
500
|
|
Luminescence lamp
|
|
2-3
|
10-15
|
-
|
-
|
8,6
|
11,5
|
17,3
|
23
|
35
|
46
|
58
|
|
15-25
|
-
|
-
|
7,3
|
9,7
|
14,5
|
19,4
|
29
|
39
|
49
|
|
25-50
|
-
|
-
|
6,0
|
8,0
|
12,0
|
16
|
24
|
32
|
40
|
|
50-150
|
-
|
-
|
5,0
|
6,7
|
10,0
|
13,4
|
20
|
27
|
34
|
|
150-300
|
-
|
-
|
4,4
|
5,9
|
8,9
|
11,8
|
17,7
|
24
|
30
|
|
More 300
|
-
|
-
|
4,1
|
5,5
|
8,3
|
11
|
16,5
|
22
|
27
|
|
Incandescent lamp (bulb lamp)
|
|
2-3
|
10-15
|
11
|
17
|
24,
|
31
|
45
|
61
|
-
|
-
|
-
|
|
15-25
|
9,2
|
14
|
20
|
25,5
|
37
|
50
|
-
|
-
|
-
|
|
25-50
|
7,8
|
12
|
17,3
|
21,5
|
31
|
42
|
-
|
-
|
-
|
|
50-150
|
6,5
|
10,3
|
14,7
|
18,5
|
27
|
36
|
-
|
-
|
-
|
|
150-300
|
5,6
|
9,2
|
12,9
|
16,3
|
24
|
32
|
-
|
-
|
-
|
|
More 300
|
5,2
|
8,2
|
12,3
|
15,3
|
22
|
29,5
|
-
|
-
|
-
|
Hygienically norms of artificial illumination
Methods of determination of the natural
lighting indices in different premises
Descriptive data:
1. External factors
that influence natural lighting in different premises:
- the territory latitude and its climate (number of sunny
and cloudy days);
- season of the year and time of the day, when the
premises are being used, existence of objects producing shadow (buildings,
trees, hills, mountains).
2. Internal
factors:
- name and function of premises;
- window orientation, floor;
- type of natural lighting, (light aperture location), (one-side,
two-side, upper and combined);
- number of windows, their construction (one-framed,
two-framed, combined);
- clarity and quality of glass, existence of objects
producing shade (flowers and curtains);
- the window-sill height, distance from the window top
edge to the ceiling;
- brightness (reflection ability) of the ceiling, walls,
equipment and furniture
The above mentioned factors also influence the premises
insolation regimen (the duration of exposure to the direct solar light). It can
also be influenced by the windows’ orientation. (table 1).
Table 1
Types of
premises isolation regimen
According to the hygienic norms the duration of insolation
in residential areas, classrooms and other premises of similar functions must
be not less than 3 hours.
The assessment of natural lighting in different premises
using thegeometric method:
1. The lighting
coefficient determination (the ratio of the glazed part area to the floor area,
expressed in common fraction);
- the total area of the glazed window part is to be
measured (S1), m2;
- the area of the floor is to be measured (S2),
m2;
- the lighting coefficient is to be measured (LC=S1:S2=1:n)(nis calculated as S2 divided on S1 and
approximated to the integer).
The received result is assessed according to the hygienic
norms (table 2).
Table 2
The natural lighting norms for different premises
2. Determination of the angle of incidence a (the ABC angle at the furthest workplace from the window
is formed by the horizontal line (or plane) AB from the workplace to the lower
window edge (window-sill) and the line (plane) AC from the workplace to the
upper window edge) (fig. 4.1).
Fig. 4.1. Diagram for determination of the angle of
incidence and the angle of aperture
The aperture angle calculation:
tga=BC/AB (see table of tangents), a - the angle of incidence;
tgb=BD/AB (see table of tangents), b - the angle of shading;
Ðg=Ða-Ðb Ðg
Conventional marks:
BC- the height from the upper window edge to the work
plane level, m;
AB- the distance from the window to the furthest work
place, m;
BD- the distance from the projection of the shadowing
object’s top onto the window glass to the level of the worktop, m.
As this angle together with the window glass line form the
right triangle, it must be determined by tangent – the ratio of the window
height above the workplace level (BC) (opposite cathetus of the triangle) to
the distance from the window to the workplace (AB) (adjacent cathetus of the
triangle). The angle of incidence a is found by
the tangent value using the table 3.
Table 3
The indoor and outdoor lighting is measured
by luxmeter (see the instruction, appendix 2 and fig. 4.2).
Fig. 4.2. Luxmeter U-116 (Ю-166)
(1 – measuring device (galvanometer); 2 – light receiver
(selenium photo-cell); 3 – changing light filters)
The part of
the sky can be hidden behind the tall buildings and trees in the cities or by
mountains in highlands. That’s why the curves of the regional lighting climate
are used in practice (fig. 4.3).
The curves, shown on the fig.4.3, include months, hours and
the level of cloudiness. The ordinate axis has lighting indicators, marked in
thousands of lux.
The natural lighting of factory
sections may be side (one-side, double-side), upper (light apertures in the
ceilings) and combined.
According to the Building Norms and Rules (BNandR)-4-79, the daylight factor (DF) is calculated:
- in case of one-sided lighting – at the distance of 1 m from the
opposite wall;
- in case of double-sided
lighting - in the middle of the section;
- in case of the combined
lighting, the average of the several lighting measurings, performed using the
“envelope” method is calculated (table 4).
Fig. 4.3. Curves of light climate
Table 4
The DF values for the industrial premises
Appendix2
TRAINING INSTRUCTION
on lighting determination using the luxmeter
The front panel of the luxmeter also contains the
switching buttons, and the scheme, that explains the effect of each button when
using different light filters. There are two different scales at the device’s
panel: the 0 – 100 scale, and the 0-30 scale. Each of them has the starting
point of its measuring range marked: on the 0-100 scale that is 20, and on the
0-30 scale – 5. Also there is the screw-adjusted regulator for setting the
device to zero.
The selenium photo-cell connected to the device with the
plug is hidden in the plastic case. The spherical light filter, made of white
light dispersing plastic and the opaque ring, is used with the photo-cell for
more exact measuring. This filter is used simultaneously with one of the three
changing filters. These changing filters have different attenuations (10, 100
and 1 000), and they extend the measuring range.
The process of the measuring consists of the following:
1) The
device is set to 0;
2) By
trying the different combinations of the pressed buttons and changing filters,
the appropriate scale for the present light is found. When the button, next to
which the ranges, divisible by 3 are written, the 0-30 scale is used. When the
button with the ranges, divisible by 10 is pressed – the 0-100 scale is used;
3) The
measuring result in scale marks is then multiplied by the attenuation value of
the filter used.
The U-116 (Ю-116) or U-117 (Ю-117) luxmeter is graded for measuring the light, produced
by the incandescent lamps. The correcting coefficients are used for the other
types of light. For the natural light its value is 0.8, for the fluorescent
daylight lamps – 0.9, and for the white lamps – 1.1.
The general assessment of the natural lighting in
different premises is made by comparing the results of all measurements with
the hygienic norms. The accuracy of visual work is the base for these norms. It
includes the sizes of the visual objects, their contrast against the background
etc.
For the convenience the results of measurements and the
hygienic norms are written into the table:
To draw the final conclusion about the natural lighting of
different premises it is necessary to compare the assessment of each result
with the norm.
PHYSICAL
CHARACTERISTICS OF ARTIFICIAL ILLUMINATION
1. The artificial illumination (same as natural) is
characterized by:
- light intensity
(I)- the light source capacity, measured in candles
(Cd). It’s a light intensity, that generates the monochrome radiation of the
540∙1012Hzfrequency
in certain direction, with radiant intensity in that direction of
1/683Wt/steradian;
- light flow
(luminous flux) (F)- the density of light, measured in lumens (lm)- light flow, radiated by the
individual source with intensity of 1 cd in the solid angle of 1 steradian. The
solid (spatial) angle is the cone, which, if its top is considered to be in the
center of the sphere, cuts the surface, equaling to the squared radius of that
sphere from it;
- illuminance
(E)- the amount of light falling on a surface (surface density of the light
flow) , where S is the illuminated surface
area, m2. The illuminance is measured in luxes. 1 lux is the illuminance of the 1 m2 surface, illuminated by the light flow of 1 lumen;
- brightness (B)
–light intensity, at which the light is radiated or reflected from the surface
in certain direction. , where is the angle between the light direction and
the perpendicular to the surface.
The unit of brightness is cd/m2- the brightness of the surface with the area of
1m2, radiating or reflecting the light with the intensity of 1cd;
- reflection
coefficient (β) - the ratio of the reflected light flow (Fref)
to the light flow received by the surface (Frec). It is calculated using
the following formula .
The β value is 0.9 for fresh snow, 0.7–for white
paper and 0.35 – for untanned skin.
- optical transmission coefficient(τ) is the
light flow, which goes through the (Fthrough.) medium, divided by
the light flow, which falls on that medium .
This coefficient allows assessing the quality and the
cleanness of the window glass and the glass parts of different
lightingfixtures.
-luminosity (M)
– surface density of the light flow, expressed in lm, which is radiated from the
1m2 surface (lm/m2).
2. HUMAN VISION
- visual acuity (the
recognition ability) is the ability of the visual analyzer to recognize the
smallest elements of the object. It’s determined by the smallest angle, under
which the two adjacent spots are recognized as separate. The visual acuity is
conventionally considered to equal to one angular minute. The visual acuity
grows proportionally to the illuminance until it reaches 130-150lux. When the
illuminance is above that point, the visual acuity growth slows down.
- contrast
sensitivity is the ability of the visual analyzer to perceive the minimum
difference between the brightness of the object and the background. It reaches
its highest level when the illuminance is 1 000-2 500 luxes;
- visual perception
speed is the time, required to recognize the details of the object. This
speed grows until the illuminance reaches 150 luxes. After that point, the
growth slows down unproportionally to the illuminance growth;
- visibilityis
the integral function of the visual analyzer, which is the combination of its
main functions – visual acuity, contrast sensitivity, visual perception speed;
- clear vision
stability is the time, during which the object can be clearly seen to the
total time of the object examination. Physiologically this function of the visual
analyzer based on the destruction of the visual purple (rhodopsin) under the
influence of the light and formation of the protective black pigment on those
parts of the retina, where the picture is the brightest. This function reaches
its optimal value at the illuminance of 600-1 000 luxes. Its reduction is
the evidence of the visual analyzer fatigue;
- color recognition
function. White, black, grey – achromatic colours are only characterized by
brightness and light flow intensity. Chromatic colours (monochromatic) are
characterized by brightness and chromaticity. Vision is the most sensitive to
the yellow and green part of the visual spectrum and the least sensitive to the
violet light. During the twilight or under the artificial illumination
(especially with incandescent lamps) the visual analyzer’s colour recognition
reduces and may distort;
- adaptationis visual analyzer’s ability to reduce its sensitivity during the change
from low to high illumination (light adaptation), (achieved very quickly, (in
2-3 minutes) and is caused by the visual purple conversion into the protective
black pigment in the retina), and to increase it again when the illumination
changes from high to low level (adaptation to darkness), which takes much
longer – up to 40-60 minutes and is caused by the restoration of the visual
purple in the retina;
- accommodationisthe
ability of the eye to regulate the visual acuity depending on the distance to
the examined object and illumination due to the changes in the light refraction
in the optic system of the eye, which is mostly caused by the chrystalline lens
curvature change. The curvature will increase when the illumination is less than
100-75luxes. So, in such circumstances the object must be closer to the eye for
the proper recognition;
The insufficient illumination leads to the overstrain of
accommodation system, overstrain of the visual analyzer, and for children and
adolescents (their eye has not yet formed completely) it may cause the myopia
(short-sightedness) especially if they have the congenital disposition;
- critical flicker
frequency is determined by the time, during which the afterimage remains in
the visual analyzer: the image of an object, which has disappeared from the
visual field still remains visible for some time depending on the object
brightness. This visual function is based on the same processes of visual purple
destruction and restoration. The cinema, one of the most important human
inventions, is based on it. The frequent change of the frames and the almost
similar objects (25 frames per second), and the darkening of the screen
provides dynamic and continuous picture.
The sources of artificial illumination may be electric and
non-electric. Non-electric sources are kerosene, carbide lamps, candles and gas
lamps. Their use nowadays is mostly limited to the field conditions and
emergency situations. The electric sources of artificial illumination may be
arc lamps (in searchlights, floodlights, spotlights etc), incandescent lamps,
gas-discharge lamps and luminescent lamps.
The disadvantage of incandescent lamps is the spectrum
parallax in the yellow-red direction, the distortion of the color perception,
the dazzling (blinding) effect of direct rays.
The luminescent lamps have the spectrum, almost similar to
the day light with modifications, depending on the luminophor, that covers the
internal surface of the glass tube and transforms the ultraviolet luminescence
of mercury vapour in the tube into the visible light. There are the daylight
lamps (DL), white light lamps (WL), warm white light lamps (WWL) etc.
The disadvantage of luminescent lamps is the stroboscopic
effect - the flickering of moving objects.
One of the disadvantages of both the direct sunlight and
bright sources of artificial illumination is their ability to cause the
dazzling effect. We protect ourselves from the bright sunlight using the
curtains and jalousies, dark-toned windows, the sun glasses.
The lighting fixtures (also used for the aesthetic
purpose), are used for protection from the dazzling effect of artificial light
sources.
The lighting fixtures are divided onto 5 types according
to light flow formation (see fig. 5.1):
- direct light type, directing the whole light flow into
one hemisphere (the table lamp with the opaque lamp-shade, spotlights,
floodlights, and other fixtures used in photo and movie shooting);
- evenly-diffusing the light (dim or light-white sphere);
- reflected light (when the lamp with the opaque
lamp-shade directs the light flow towards the upper hemisphere);
- directed-diffused light type, when the main light flow
is directed towards the lower hemisphere through the aperture in the lamp-shade
and the other part is diffused to the upper hemisphere through the lamp-shade
made of plastic, dim or light-white glass;
- reflected-diffused light type, when the main light flow
is directed towards the upper hemisphere and is reflected from the ceiling but
a part of it is diffused to the lower hemisphere through the lamp-shade with
dim or light-white glass.
The allowable values of dazzling at the workplace are:
-20 cd/m2 for types 1 and 2 of the visual work;
-40 cd/m2 for the types 3-5 of the visual work;
- 60 cd/m2 for the types 6 and 7 of the visual
work.
Fig.5.1. Types of lighting fixtures
(1 - direct light type, 2 - directed-diffused light type;
3, 4 - evenly-diffused light type;
5 - reflected-diffused light type)
The scheme of the artificial illumination assessment in
different premises
Descriptive data:
-
name and function of premises;
-
system of illumination (local, general and combined);
-
number of lights, their types (incandescent, luminescent and other lamps);
-
their capacity, Wt;
-
type of lighting fixture, light flow direction and formation (direct,
evenly-diffused, directed-diffused, reflected, diffused-reflected);
-
height of the lamps above the floor and the work plane;
- illuminated area;
- reflection ability
(brightness) of ceiling, walls, windows, floor, furniture and other surfaces.
Illumination
determination using the ‘Watt’ calculation method:
a) the
area of the premises is determined, S, m2;
b) the
total capacity of all the lamps, Wt, is determined;
c) the
specific capacity, Wt/ m2, is calculated;
d) the
illuminance at the specific capacity of 10Wt/m2 can be found from
the table 1 of minimum horizontal illuminance values;
e) for
the incandescent lamps the illuminance is calculated according to the following
formula:
where, P –is
a specific capacity, Wt/m2;
Etab- illuminance at 10Wt/m2, (from
table 1);
K – which equals
to 1.3, is the reserve coefficient for residential and public premises.
Table 1
The (Etab) minimum horizontal illuminance
values at the specific capacity (P) of 10 Wt/m2
This formula may be applied for the illumination
calculation if all the lamps have the same capacity.The calculations are done
separately if there are lamps with different capacity. Their results are added
up. The received illumination value by the “Watt” method is compared to the
normative values (table 2).
Table 2
Standards of
the general artificial illumination (BNaR II-69-78 and BNaR II-4-79)
For the luminescent lamps with 10 Wt/m2
specific capacity the minimum horizontal illumination is 100 luxes. The minimum
horizontal illumination for other specific capacities is calculated
proportionally.
For the industrial areas, according to BNandR II-4-79, all
activities are divided into seven types of work, based on the linear dimensions
of the smallest object, worked with at the distance of 0.5 m from the eye. The
first 5 types are divided into 4 sub-types (a, b, c, d), based on the contrast
between the examined object and the background, and the background luminosity.
For example, during the especially accurate work (type 1, the object size is
less than 0.1 mm), the illumination at the workplace must be 1 500luxes if
the contrast with the background is low; 1 000 luxes if the contrast is
medium and 400 luxes if the contrast is high. When the work is of low accuracy
(type 4, object size is 1.0-10 mm ), the illumination must be 150,100, 75luxes
respectively.
The above mentioned method is not fully precise as it doesn’t
take the illumination in each point, lamp location and some other factors into
the account, but is often used for the classes, wards and other areas
illumination assessment.
To determine the illumination at the definite workplace,
the lamp specific capacity (P) must be multiplied by the coefficient (e), which
shows the amount of luxes, given by the 1 Wt/m2 specific capacity:
E=P×e. This coefficient for the premises of 50m2 area and the
lamp capacities of less than 110 Wt is 2, 110 Wt and more – 2.5 (see table 3)
and 12.5 for the luminescent lamps.
Table 3
The values of the coefficient e
Illuminance determination using the luxmeter.
The determination of horizontal illuminance at the workplace
is done with the help of luxmeter (see topic 4, appendix 2). The 0.9 correction
coefficient is used for the luminescent lamps of day illumination (LD); 1.1 -
for the white lamps; 1.2-for the mercury-discharge lamps, because the device
has initially been intended for measuring of the illuminance, produced by
incandescent lamps.
If the determination is done in the morning or in the
afternoon, it’s necessary to determine the illuminance, produced by the mixed
illumination (both natural and artificial). After that the determination is
done when the artificial illumination is switched off. The difference between
the received data is the value of illuminance, produced by the artificial
illumination.
The illumination evenness is determined by the “Envelope
method,” which means that illuminance is measured at 5 different points of the
premises and evaluated by calculation of illuminance variety coefficient
(minimum illuminance divided by the maximum illuminance at two different
points, which are 0.75 m from each other, when the evenness is determined at
the workplace, or 5 m from each other, if the evenness is determined in the
whole room).
The calculation of the workplane brightness is made
using to the formula:
where,B-is brightness, cd/m2;
E-illumination, lux;
C-coefficient of surface reflection
(0.7-white; 0.5 - light-beige; 0.4-brown; 0.1-black).
The allowable brightness of general illumination lamps for
residential and public premises is given in the table 4.
Table4
The allowable brightness values of general illumination
lamps for residential and public premises
The height of the lamps above the floor and the working place,
and the location of general light lamps in the horizontal plane of premises is
of the great importance for creating the sufficient and even illumination, and
for the protection from dazzling. When the illumination is general or combined,
the lamps of general light are located evenly in the horizontal plane of the
ceiling (when it is necessity to create sufficient illuminance in every point
of premises), or they are locally concentrated (to create the high illuminance
in certain parts of the room). The lamp height above the floor must be not
lower, than values, given in the table 5 to minimize the dazzling effect of the
lamps.
The best illumination conditions are created when the
optimal ratio between the distance between the lamps in horizontal plane (L),
and their height above the work-plane (H) is used. These ratios have been found
as a result of the determination of the light distribution curves of different
lamps. The optimal values are shown in table 6.
Table 5
The lowest height of the lamps above the floor (m)
Table 6
The optimal ratios between the distance between the lamps
and their height above the work-plane (L/H)
REFERENCES:
Principal:
1.
Hygiene
and human ecology. Manual for the students of higher medical institutions/
Under the general editorship of V.G. Bardov. – K., 2009. – PP. 14-34, 71-106.
2.
Datsenko
I.I., Gabovich R.D .Preventive medicine. - K.: Health, 2004, pp. 14-74.
3.
Lecture
on hygiene.
additional:
1.
Kozak
D.V., Sopel O.N., Lototska O.V. General Hygiene and Ecology. – Ternopil: TSMU,
2008. – 248 p.
2.
Dacenko
I.I., Denisuk O.B., Doloshickiy S.L. General hygiene: Manual for practical studies. -Lviv: Svit, 2001. - P. 6-23.
3.
A
hand book of Preventive and Social Medicine. – Yash Pal Bedi / Sixteenth
Edition, 2003 – p. 26-36,
92-97.
