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Chemical composition of air
Atmospheric air is a mixture of various gases. It contains constant atmospheric components (oxygen, nitrogen, carbon dioxide), inert gases (argon, helium, neon, krypton, hydrogen, xenon, radon), small amounts of ozone, nitrous oxide, methane, iodine, water vapor, and in variable quantities, various impurities of natural origin and pollution resulting from human production activities.
Oxygen (O2) is the most important part of air for humans. It is necessary for the implementation of oxidative processes in the body. In atmospheric air, the oxygen content is 20.95%, in the air exhaled by man - 15.4-16%. Its decrease in atmospheric air to 13-15% leads to a violation of physiological functions, and to 7-8% - to death.
Nitrogen (N) - is the main component of atmospheric air. The air inhaled and exhaled by a person contains approximately the same amount of nitrogen - 78.97-79.2%. The biological role of nitrogen lies mainly in the fact that it is an oxygen diluent, since life is impossible in pure oxygen. With an increase in nitrogen content to 93%, death occurs.
Carbon dioxide (carbon dioxide), CO2 - is a physiological regulator of respiration. The content in clean air is 0.03%, in the exhaled person - 3%.
A decrease in the concentration of CO2 in the inhaled air is not dangerous, because its necessary level in the blood is supported by regulatory mechanisms due to excretion during metabolic processes.
Increasing the carbon dioxide content in the inhaled air to 0.2% causes a person to feel unwell, with 3-4% there is an excited state, headache, tinnitus, palpitations, slow heart rate, and at 8% severe poisoning, loss of consciousness and death comes.
Recently, the concentration of carbon dioxide in the air of industrial cities has been increasing as a result of intense air pollution by fuel combustion products. The increase in atmospheric CO2 leads to the appearance of toxic fogs in cities and the “greenhouse effect” associated with carbon dioxide delayed thermal radiation of the earth.
The CO2 content in the air serves as an important hygienic indicator for judging the purity of air in industrial, residential and public buildings. The maximum permissible concentration of carbon dioxide in the premises is 0.1%. This value is taken as the calculated value when determining the ventilation efficiency.
An increase in CO2 content above the established norm indicates a general deterioration in the sanitary state of the air, because along with carbon dioxide other toxic substances can accumulate, the ionization regime may deteriorate, dustiness and microbial contamination may increase.
Ozone (O3). Its main amount is noted at the level of 20-30 km from the Earth's surface. The surface layers of the atmosphere contain a negligible amount of ozone - not more than 0.000001 mg / l. Ozone protects the living organisms of the earth from the harmful effects of short-wave ultraviolet radiation and at the same time absorbs the long-wave infrared radiation emanating from the Earth, protecting it from excessive cooling. Ozone has oxidizing abilities, therefore, its concentration in the polluted air of cities is lower than in rural areas. In this regard, ozone was considered an indicator of air purity. However, it has recently been established that ozone is formed as a result of photochemical reactions during the formation of smog, therefore, the detection of ozone in the atmospheric air of large cities is considered an indicator of its pollution.
Inert gases - do not have a pronounced hygienic and physiological value.
Human economic and industrial activity is a source of air pollution by various gaseous impurities and suspended particles. The increased content of harmful substances in the atmosphere and in indoor air adversely affects the human body. In this regard, the most important hygienic task is the rationing of their permissible content in the air.
The sanitary-hygienic condition of the air is usually evaluated by the maximum permissible concentrations (MPC) of harmful substances in the air of the working area.
The maximum permissible concentration of harmful substances in the air of the working area is the concentration which, during daily 8-hour work, but not more than 41 hours a week, during the entire working experience does not cause diseases or deviations in the state of health of the present and subsequent generations.
Set the maximum daily concentration limit and the maximum one-time (action up to 30 minutes in the air of the working area). MPC for the same substance may be different depending on the duration of its exposure to humans.
At food enterprises, the main causes of air pollution by harmful substances are process violations and emergency situations (sewage, ventilation, etc.).
Hygienic hazards in indoor air are carbon monoxide, ammonia, hydrogen sulfide, sulfur dioxide, dust, etc., as well as air pollution by microorganisms.
Carbon monoxide (CO) is an odorless and colorless gas that enters the air as a product of incomplete combustion of liquid and solid fuels. It causes acute poisoning at a concentration in the air of 220-500 mg / m3 and chronic poisoning - with constant inhalation of a concentration of 20-30 mg / m3. The average daily maximum permissible concentration of carbon monoxide in atmospheric air is 1 mg / m3, in the air of the working zone - from 20 to 200 mg / m3 (depending on the duration of work).
Sulfur dioxide (S02) is the most common admixture of atmospheric air, since sulfur is found in various fuels. This gas has a general toxic effect and causes respiratory diseases. The irritating effect of the gas is detected when its concentration in the air exceeds 20 mg / m3. In atmospheric air, the daily average MAC of sulfur dioxide is 0.05 mg / m3, in the air of the working zone - 10 mg / m3.
Hydrogen sulfide (H2S) - usually enters the atmospheric air with waste from chemical, oil refining and metallurgical plants, and also forms and can pollute indoor air as a result of rotting food waste and protein products. Hydrogen sulfide has a general toxic effect and causes unpleasant sensations in humans at a concentration of 0.04-0.12 mg / m3, and a concentration of more than 1000 mg / m3 can become fatal. In atmospheric air, the average daily MPC of hydrogen sulfide is 0.008 mg / m3, in the air of the working zone - up to 10 mg / m3.
Ammonia (NH3) - accumulates in the air of enclosed spaces during the decay of protein products, malfunctions of refrigeration units with ammonia cooling, during accidents of sewage systems, etc. Toxic to the body.
Acrolein - a product of fat decomposition during heat treatment, is capable of causing allergic diseases in a production environment. MPC in the working area - 0.2 mg / m3.
Polycyclic aromatic hydrocarbons (PAHs) - their connection with the development of malignant neoplasms is noted. The most common and most active of them is 3-4-benz (a) pyrene, which is released during the combustion of fuel: coal, oil, gasoline, gas. The maximum amount of 3-4-benz (a) pyrene is released during the combustion of coal, the minimum - during the combustion of gas. In food establishments, the source of PAH air pollution can be the prolonged use of superheated fat. The daily average MPC of cyclic aromatic hydrocarbons in the air should not exceed 0.001 mg / m3.
Mechanical impurities - dust, particles of soil, smoke, ash, soot. Dustiness increases with insufficient landscaping, poor access roads, violation of the collection and removal of industrial waste, as well as violation of the sanitary regime of cleaning the premises (dry or irregular wet cleaning, etc.). In addition, the dustiness of the premises increases with violations in the arrangement and operation of ventilation, planning decisions (for example, with insufficient isolation of the vegetable pantry from production shops, etc.).
Human exposure to dust depends on the size of the dust particles and their specific gravity. Dust particles smaller than 1 micron in diameter are most dangerous to humans, as they easily penetrate the lungs and can cause their chronic disease (pneumoconiosis). Dust containing impurities of toxic chemical compounds has a toxic effect on the body.
The maximum permissible concentration of soot and soot is strictly standardized due to the content of carcinogenic hydrocarbons (PAHs): the average daily maximum concentration of soot is 0.05 mg / m3.
In confectionery shops of high power dustiness of air with sugar and flour dust is possible. Flour dust in the form of aerosols can cause respiratory irritation, as well as allergic diseases. The maximum permissible concentration of flour dust in the working area should not exceed 6 mg / m3. Within these limits (2-6 mg / m3), the maximum permissible concentrations of other types of plant dust containing not more than 0.2% silicon compounds are regulated.
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Chemical composition of air
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and oxygen СО2 (carbon dioxide) N2 (nitrogen) Inert gases and impurities 20.94% 0.03-0.04% 78.1% 1% The biological significance of oxygen lies in participation in respiration, which is necessary for oxidative processes in the body. A person absorbs 12 liters of oxygen per hour or 6-7 liters of air per minute, athletes - up to 120 liters per hour. It is given by: - atmosphere - green (chlorophyll) plants. Indoors
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