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Physical properties of air


The temperature on the earth ranges from -940С to + 630С. Temperature conditions depend on the latitude of the area: the farther from the equator, the sharper the angle of incidence, therefore, the earth heats less. On the surface (near the ground) the layers of air are warmer, every 100m the air temperature drops by 0.5 ° C.
Thanks to the thermoregulatory mechanisms that are controlled by the central nervous system, a person adapts to various temperature conditions.
At a low temperature, the vessels narrow and the blood goes inside to the organs - possibly external hypothermia. At high temperature - the vessels expand and heat is transferred from the surface.
When the temperature controllers do not cope, hypothermia or overheating, leading to deep pathological disorders, occurs.
High air temperature (above 350C) causes:
- increase in body temperature (heat transfer is difficult);
- increased breathing and pulse;
- weakening of the compensatory ability of the cardiovascular system (due to an increase in blood viscosity - perspiration is possible up to 5-8 l / day);
- a change in metabolism (water-salt balance is disturbed);
- decrease in the functional activity of the gastrointestinal tract;
- headache;
- loss of appetite;
- reduced attention, accuracy, coordination of movements, reaction speed, ability to quickly switch, therefore, injuries, damage during sports and work;
- a negative impact on the functional state of the central nervous system - fatigue, decreased physical and mental MS, heat stroke, so clothing should be appropriate.
In a hot climate, the body weakens and becomes more susceptible to infectious diseases (due to a decrease in the immunobiological reactivity of the body).
At low air temperatures:
- heat transfer increases (danger of hypothermia);
- skin temperature decreases.
Strong exposure to low temperatures causes
a) a variety of reflex reactions (legs froze, as a result of a runny nose, cough, tonsillitis);
b) cooling of peripheral nerves, muscles and ligaments - as a result, rheumatism, sciatica, neuritis.
In sports: “narcotic” action of cold (decrease in reaction to pain). The elasticity and contractility of the muscles and ligaments are reduced, therefore injuries are possible (below 10 0С).
Moderate temperature fluctuations are not harmful and provide physiological training of the body and thermoregulatory mechanisms.
The phenomenon of hypothermia can be prevented, and it is more difficult to protect yourself from overheating.
Hygienic norms of air in the room: 18-20 0С - at normal humidity. Hygienically unfavorable above 24-25 0С; violate thermal equilibrium below 14-15 0C.
In sports: sports hall - 14-16 0С
pool - 25-27 0С (1-20С higher than t 0 water) athletics arena -15-17 0С wrestling -16-18 0С
gymnastics -15 (high class) -18 0С (beginners) massage - 22 0С locker rooms - up to 25 0С
In the open air in summer, a favorable temperature = 18-20 ° C (for training no more than 22-250 ° C, wind no more than 5 m / s).
Humidity - the content (in grams) of water vapor in 1 m3 of air (measured by the height of the mercury column in millimeters). Each air temperature corresponds to a certain limiting degree of saturation with water vapor: the higher the temperature, the more water vapor can be contained in it.
Exist:
- absolute humidity (at this time, at a given temperature);
- maximum humidity (complete saturation of air with vapors at a given temperature);
- deficiency of saturation (the difference between the maximum and absolute humidity);
- dew point (temperature at which water vapor in the air saturates the space).
In hygiene is used:
- relative humidity (the ratio of absolute humidity to maximum and expressed as a percentage).
A person loses through the skin: 0.4 - 0.6 l of water per day. Evaporation of 1 gram of water takes 0.6 kcal. During intense sports, there are losses of up to 5-6 liters of water per day.
Type of relative humidity and its indicator: high humidity - 90% and higher; moderate humidity - 70 - 90%; average - 20-70%; low humidity - 20% and lower.
High humidity at a temperature below 10-15 0 reduces immunity to colds and infections. The connection of such conditions with the development of rheumatism, pulmonary tuberculosis, and kidney disease is especially clearly established.
The high temperature in Central Asia, reaching 40,450 in the shade in summer, is easier to tolerate due to low humidity (10-15%).
The body carries dry air more easily than moist air.
Normal indoor humidity is considered to be 30-60%. During physical work and at air temperatures below 200 or below 150, air humidity should not exceed 30-40%, and at temperatures above 250
- 20-25%. Otherwise, thirst and drying out of the mucous membranes is possible. The humidity rate for a living room is 30-60%; for the gym
- 40 - 55%.
The biological effect of humidity is to influence the thermoregulation and hydration of the mucous membranes.
Air movement (air mobility) is characterized by:
1. direction (where the wind blows - rumb)
2. speed (meters per second or points).
A graphic depiction of wind recurrence in a given area is called a wind rose. The table shows the indicators of air velocity.
Beaufort air performance
Wind speed m / s Points Power
wind characteristic
Visual assessment
(N
o '
1
ABOUT
0 calm smoke rises vertically, leaves are motionless
0.3 - 1.5 1 quiet smoke deviates slightly
1.6 - 3.3 2 easy leaves rustle, the movement of air is felt by the face
3.4 - 5.4 3 weak leaves and thin branches of trees sway
5.5 - 7.9 4 moderate raises dust, tree tops bend
8.0 - 10.7 5 fresh thin trunks swing
10.8 - 13.8 6 strong thick trunks swing, telephone wires buzz
13.9 - 17.1 7 strong shakes everything, going against the wind is hard
17.2 - 20.7 8 very strong breaks small branches, it’s very hard to walk
20.8 - 24.4 9 storm minor damage to buildings, destruction
24.5 - 28.4 10 heavy storm trees uprooting, large damage to buildings
28.5 - 32.6 eleven fierce storm great destruction
32.7 and more 12 Hurricane devastating destruction




The hygienic significance of air movement mainly lies in its ability to increase heat transfer by convection.
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Physical properties of air

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