Air composition in percentage by volume diagram. All about atmospheric air

The lower layers of the atmosphere consist of a mixture of gases called air , in which liquid and solid particles are suspended. The total mass of the latter is insignificant in comparison with the entire mass of the atmosphere.

Atmospheric air is a mixture of gases, the main of which are nitrogen N2, oxygen O2, argon Ar, carbon dioxide CO2 and water vapor. Air without water vapor is called dry air. At the earth's surface, dry air is 99% nitrogen (78% by volume or 76% by mass) and oxygen (21% by volume or 23% by mass). The remaining 1% is almost entirely argon. Only 0.08% remains for carbon dioxide CO2. Numerous other gases are part of the air in thousandths, millionths and even smaller fractions of a percent. These are krypton, xenon, neon, helium, hydrogen, ozone, iodine, radon, methane, ammonia, hydrogen peroxide, nitrous oxide, etc. The composition of dry atmospheric air near the Earth's surface is given in table. 1.

Table 1

Composition of dry atmospheric air near the Earth's surface

	Volume concentration, %	Molecular mass	Density relative to density dry air
Oxygen (O2)
Carbon dioxide (CO2)
Krypton (Kr)
Hydrogen (H2)
Xenon (Xe)
Dry air

The percentage composition of dry air near the earth's surface is very constant and almost the same everywhere. Only the carbon dioxide content can change significantly. As a result of the processes of breathing and combustion, its volumetric content in the air of closed, poorly ventilated rooms, as well as industrial centers, can increase several times - up to 0.1-0.2%. The percentage of nitrogen and oxygen changes quite slightly.

The real atmosphere contains three important variable components - water vapor, ozone and carbon dioxide. The content of water vapor in the air varies within significant limits, unlike other components of the air: at the earth's surface it fluctuates between hundredths of a percent and several percent (from 0.2% in polar latitudes to 2.5% at the equator, and in some cases ranges from almost zero to 4%). This is explained by the fact that, under the conditions existing in the atmosphere, water vapor can transform into liquid and solid states and, conversely, can enter the atmosphere again due to evaporation from the earth’s surface.

Water vapor continuously enters the atmosphere through evaporation from water surfaces, from moist soil and through transpiration of plants, in different places and in different time it comes in varying quantities. It spreads upward from the earth's surface, and is transported by air currents from one place on the earth to another.

A saturation state may occur in the atmosphere. In this state, water vapor is contained in the air in the amount that is maximum possible at a given temperature. Water vapor is called saturating(or saturated), and the air containing it saturated.

The saturation state is usually reached when the air temperature decreases. When this state is reached, then with a further decrease in temperature, part of the water vapor becomes excess and condenses, turns into a liquid or solid state. Water droplets and ice crystals of clouds and fogs appear in the air. Clouds may evaporate again; in other cases, droplets and crystals of clouds, becoming larger, can fall onto the earth's surface in the form of precipitation. As a result of all this, the content of water vapor in each part of the atmosphere is constantly changing.

With water vapor in the air and its transitions from gaseous state The most important weather processes and climate features are connected to liquid and solid. The presence of water vapor in the atmosphere significantly affects the thermal conditions of the atmosphere and the earth's surface. Water vapor strongly absorbs long-wave infrared radiation emitted by the earth's surface. In turn, it itself emits infrared radiation, most of which goes to the earth's surface. This reduces the night cooling of the earth's surface and thus also the lower air layers.

Large amounts of heat are expended on the evaporation of water from the earth's surface, and when water vapor condenses in the atmosphere, this heat is transferred to the air. Clouds resulting from condensation reflect and absorb solar radiation on its way to the earth's surface. Precipitation from clouds is an essential element of weather and climate. Finally, the presence of water vapor in the atmosphere is important for physiological processes.

Water vapor, like any gas, has elasticity (pressure). Water vapor pressure e is proportional to its density (content per unit volume) and its absolute temperature. It is expressed in the same units as air pressure, i.e. either in millimeters of mercury, either in millibars

The pressure of water vapor at saturation is called saturation elasticity. This the maximum pressure of water vapor possible at a given temperature. For example, at a temperature of 0° the saturation elasticity is 6.1 mb . For every 10° temperature increase, the saturation elasticity approximately doubles.

If the air contains less water vapor than is needed to saturate it at a given temperature, you can determine how close the air is to the saturation state. To do this, calculate relative humidity. This is the name given to the ratio of actual elasticity e water vapor in the air to saturation elasticity E at the same temperature, expressed as a percentage, i.e.

For example, at a temperature of 20° the saturation pressure is 23.4 mb. If the actual vapor pressure in the air is 11.7 mb, then the relative humidity is

The elasticity of water vapor at the earth's surface varies from hundredths of a millibar (at very low temperatures in winter in Antarctica and Yakutia) up to 35 mb more (at the equator). The warmer the air, the more water vapor it can contain without saturation and, therefore, the greater the water vapor pressure in it.

Relative air humidity can take on all values ​​- from zero for completely dry air ( e= 0) to 100% for saturation condition (e = E).

The main components of atmospheric air are oxygen (about 21%), nitrogen (78%), carbon dioxide (0.03-0.04%), water vapor, inert gases, ozone, hydrogen peroxide (about 1%).

Oxygen is the most component air. With its direct participation, all oxidative processes occur in the human and animal body. At rest, a person consumes approximately 350 ml of oxygen per minute, and in severe physical work the amount of oxygen consumed increases several times.

Inhaled air contains 20.7-20.9% oxygen, and exhaled air contains about 15-16%. Thus, body tissues absorb about 1/4 of the oxygen present in the inhaled air.

In the atmosphere, the oxygen content does not change significantly. Plants absorb carbon dioxide and, breaking it down, assimilate carbon, and release the released oxygen into the atmosphere. The source of oxygen formation is also the photochemical decomposition of water vapor in the upper layers of the atmosphere under the influence of ultraviolet radiation from the sun. In ensuring a constant composition of atmospheric air, mixing of air flows in the lower layers of the atmosphere is also important. The exception is hermetically sealed rooms, where, due to prolonged stay of people, the oxygen content can be significantly reduced (submarines, shelters, pressurized aircraft cabins, etc.).

For the body, the partial pressure of oxygen is important, and not its absolute content in the inhaled air. This is due to the fact that the transition of oxygen from alveolar air to blood and from blood to tissue fluid occurs under the influence of differences in partial pressure. The partial pressure of oxygen decreases with increasing altitude above sea level (Table 1).

Table 1. Partial pressure of oxygen at different altitudes

Great importance has the use of oxygen for the treatment of diseases accompanied by oxygen starvation (oxygen tents, inhalers).

Carbon dioxide. The carbon dioxide content in the atmosphere is fairly constant. This constancy is explained by its cycle in nature. Despite the fact that the processes of decay and vital activity of the body are accompanied by the release of carbon dioxide, a significant increase in its content in the atmosphere does not occur, since carbon dioxide is absorbed by plants. In this case, carbon is used to build organic matter, and oxygen enters the atmosphere. Exhaled air contains up to 4.4% carbon dioxide.

Carbon dioxide is a physiological stimulant of the respiratory center, therefore during artificial respiration it is added to the air in small quantities. IN large quantities it can have narcotic effects and cause death.

Carbon dioxide also has hygienic significance. Based on its content, the cleanliness of the air in residential and public premises (i.e., premises where people are present) is judged. When people gather in poorly ventilated rooms, parallel to the accumulation of carbon dioxide in the air, the content of other human waste products increases, the air temperature rises and its humidity increases.

It has been established that if the carbon dioxide content in indoor air exceeds 0.07-0.1%, then the air acquires an unpleasant odor and can disrupt the functional state of the body.

The parallelism of the changes in the listed properties of air in residential premises and the increase in the concentration of carbon dioxide, as well as the ease of determining its content, make it possible to use this indicator for the hygienic assessment of air quality and the efficiency of ventilation of public premises.

Nitrogen and other gases. Nitrogen is basic integral part atmospheric air. In the body, it is dissolved in the blood and tissue fluids, but does not take part in chemical reactions.

It has now been experimentally established that under conditions of high pressure, air nitrogen causes a disorder of neuromuscular coordination in animals, followed by agitation and a narcotic state. Researchers observed similar phenomena among divers. The use of a helio-oxygen mixture for breathing by divers makes it possible to increase the depth of descent to 200 m without pronounced symptoms of intoxication.

During electrical lightning discharges and under the influence of ultraviolet rays from the sun, small amounts of other gases are formed in the air. Hygienic value there are relatively few of them.

* The partial pressure of a gas in a mixture of gases is the pressure that a given gas would produce if it occupied the entire volume of the mixture.

Composition of the Earth. Air

Air is a mechanical mixture of various gases that make up the Earth's atmosphere.

Air is necessary for the respiration of living organisms and is widely used in industry.

The ratio of gases in the earth's atmosphere indicated in the table is typical for its lower layers, up to an altitude of 120 km. In these areas lies a well-mixed, homogeneous region called the homosphere. Above the homosphere lies the heterosphere, which is characterized by the decomposition of gas molecules into atoms and ions. The regions are separated from each other by a turbo pause.

The chemical reaction in which molecules are decomposed into atoms under the influence of solar and cosmic radiation is called photodissociation. The decay of molecular oxygen produces atomic oxygen, which is the main gas of the atmosphere at altitudes above 200 km. At altitudes above 1200 km, hydrogen and helium, which are the lightest of the gases, begin to predominate.

Since the bulk of the air is concentrated in the 3 lower atmospheric layers, changes in air composition at altitudes above 100 km do not have a noticeable effect on general composition atmosphere.

Nitrogen is the most common gas, accounting for more than three-quarters of the Earth's air volume. Modern nitrogen was formed by the oxidation of the early ammonia-hydrogen atmosphere by molecular oxygen, which is formed during photosynthesis. Currently not a large number of nitrogen enters the atmosphere as a result of denitrification - the process of reduction of nitrates to nitrites, with the subsequent formation of gaseous oxides and molecular nitrogen, which is produced by anaerobic prokaryotes. Some nitrogen enters the atmosphere during volcanic eruptions.

In the upper layers of the atmosphere, when exposed to electrical discharges with the participation of ozone, molecular nitrogen is oxidized to nitrogen monoxide:

N 2 + O 2 → 2NO

Under normal conditions, the monoxide immediately reacts with oxygen to form nitrous oxide:

2NO + O 2 → 2N 2 O

Nitrogen is essential chemical element earth's atmosphere. Nitrogen is part of proteins and provides mineral nutrition to plants. It determines the rate of biochemical reactions and plays the role of an oxygen diluent.

The second most common gas in the Earth's atmosphere is oxygen. The formation of this gas is associated with the photosynthetic activity of plants and bacteria. And the more diverse and numerous photosynthetic organisms became, the more significant the process of oxygen content in the atmosphere became. A small amount of heavy oxygen is released during degassing of the mantle.

In the upper layers of the troposphere and stratosphere, under the influence of ultraviolet solar radiation (we denote it as hν), ozone is formed:

O 2 + hν → 2O

As a result of the same ultraviolet radiation, ozone decomposes:

O 3 + hν → O 2 + O

О 3 + O → 2О 2

As a result of the first reaction, atomic oxygen is formed, and as a result of the second, molecular oxygen is formed. All 4 reactions are called the “Chapman mechanism”, named after the British scientist Sidney Chapman who discovered them in 1930.

Oxygen is used for the respiration of living organisms. With its help, oxidation and combustion processes occur.

Ozone serves to protect living organisms from ultraviolet radiation, which causes irreversible mutations. The highest concentration of ozone is observed in the lower stratosphere within the so-called.

ozone layer or ozone screen, lying at altitudes of 22-25 km. The ozone content is small: at normal pressure, all the ozone in the earth's atmosphere would occupy a layer only 2.91 mm thick.

The formation of the third most common gas in the atmosphere, argon, as well as neon, helium, krypton and xenon, is associated with volcanic eruptions and the decay of radioactive elements.

In particular, helium is a product of the radioactive decay of uranium, thorium and radium: 238 U → 234 Th + α, 230 Th → 226 Ra + 4 He, 226 Ra → 222 Rn + α (in these reactions the α-particle is the helium nucleus, which in During the process of energy loss, it captures electrons and becomes 4 He).

Argon is formed during the decay of the radioactive isotope of potassium: 40 K → 40 Ar + γ.

Neon escapes from igneous rocks.

Krypton is formed as the end product of the decay of uranium (235 U and 238 U) and thorium Th.

The bulk of atmospheric krypton was formed in the early stages of the Earth's evolution as a result of the decay of transuranic elements with a phenomenally short half-life or came from space, where the krypton content is ten million times higher than on Earth.

Xenon is the result of the fission of uranium, but the bulk of this gas remains from the early stages of the formation of the Earth, from the primordial atmosphere.

Hydrogen is formed as a result of the decomposition of water by solar radiation. But, being the lightest of the gases that make up the atmosphere, it constantly evaporates into outer space, and therefore its content in the atmosphere is very small.

Water vapor is the result of the evaporation of water from the surface of lakes, rivers, seas and land.

The concentration of the main gases in the lower layers of the atmosphere, with the exception of water vapor and carbon dioxide, is constant. In small quantities the atmosphere contains sulfur oxide SO 2, ammonia NH 3, carbon monoxide CO, ozone O 3, hydrogen chloride HCl, hydrogen fluoride HF, nitrogen monoxide NO, hydrocarbons, mercury vapor Hg, iodine I 2 and many others. In the lower atmospheric layer, the troposphere, there is always a large amount of suspended solid and liquid particles.

The sources of particulate matter in the Earth's atmosphere are volcanic eruptions, plant pollen, microorganisms, and Lately and human activities, such as the burning of fossil fuels during production. Smallest particles dust, which are condensation nuclei, cause the formation of fogs and clouds. Without particulate matter constantly present in the atmosphere, precipitation would not fall on Earth.

It is important in the implementation of respiratory function. Atmospheric air is a mixture of gases: oxygen, carbon dioxide, argon, nitrogen, neon, krypton, xenon, hydrogen, ozone, etc. Oxygen is the most important. At rest, a person absorbs 0.3 l/min. During physical activity, oxygen consumption increases and can reach 4.5–8 l/min. Fluctuations in the oxygen content in the atmosphere are small and do not exceed 0.5%. If the oxygen content decreases to 11-13%, symptoms of oxygen deficiency appear. Oxygen content of 7-8% can lead to death. Carbon dioxide is colorless and odorless, formed during respiration and decay, combustion of fuel. In the atmosphere it is 0.04%, and in industrial zones – 0.05-0.06%. With a large crowd of people it can increase to 0.6 - 0.8%. With prolonged inhalation of air containing 1-1.5% carbon dioxide, a deterioration in health is noted, and with 2-2.5% - pathological changes. At 8-10% loss of consciousness and death, the air has a pressure called atmospheric or barometric. It is measured in millimeters of mercury (mmHg), hectopascals (hPa), millibars (mb). Normal atmospheric pressure is considered to be at sea level at a latitude of 45˚ at an air temperature of 0˚C. It is equal to 760 mmHg. (The air in a room is considered to be of poor quality if it contains 1% carbon dioxide. This value is accepted as a calculated value when designing and installing ventilation in rooms.

Air pollution. Carbon monoxide is a colorless and odorless gas that is formed during incomplete combustion of fuel and enters the atmosphere with industrial emissions and exhaust gases from internal combustion engines. In megacities, its concentration can reach 50-200 mg/m3. When smoking tobacco, carbon monoxide enters the body. Carbon monoxide is a blood and general toxic poison. It blocks hemoglobin, it loses its ability to carry oxygen to tissues. Acute poisoning occurs when the concentration of carbon monoxide in the air is 200-500 mg/m3. In this case, headache, general weakness, nausea, and vomiting are observed. The maximum permissible average daily concentration is 0 1 mg/m3, one-time – 6 mg/m3. The air can be polluted by sulfur dioxide, soot, tarry substances, nitrogen oxides, and carbon disulfide.

Microorganisms. They are always found in small quantities in the air, where they are carried with soil dust. Microbes of infectious diseases entering the atmosphere quickly die. The air in residential premises and sports facilities poses a particular danger in terms of epidemiology. For example, in wrestling halls there is a microbial content of up to 26,000 per 1m3 of air. Aerogenic infections spread very quickly in such air.

Dust It is light dense particles of mineral or organic origin; when dust gets into the lungs, it lingers there and causes various diseases. Industrial dust (lead, chrome) can cause poisoning. In cities, dust should not exceed 0.15 mg/m3. Sports grounds must be regularly watered, have a green area, and carry out wet cleaning. Sanitary protection zones have been established for all enterprises that pollute the atmosphere. In accordance with the hazard class they have different sizes: for enterprises of class 1 - 1000 m, 2 - 500 m, 3 - 300 m, 4 -100 m, 5 - 50 m. When locating sports facilities near enterprises, it is necessary to take into account the wind rose, sanitary protection zones, the degree of air pollution, etc.

One of the important measures to protect the air environment is preventive and ongoing sanitary supervision and systematic monitoring of the state of atmospheric air. It is produced using automated system monitoring.

Clean atmospheric air at the surface of the Earth has the following chemical composition: oxygen - 20.93%, carbon dioxide - 0.03-0.04%, nitrogen - 78.1%, argon, helium, krypton 1%.

The exhaled air contains 25% less oxygen and 100 times more carbon dioxide.
Oxygen. The most important component of air. It ensures the flow of redox processes in the body. An adult consumes 12 liters of oxygen at rest, and 10 times more during physical work. In the blood, oxygen is bound to hemoglobin.

Ozone. A chemically unstable gas, it is capable of absorbing solar short-wave ultraviolet radiation, which has a detrimental effect on all living things. Ozone absorbs long-wave infrared radiation emanating from the Earth, and thereby prevents its excessive cooling (Earth's ozone layer). Under the influence of ultraviolet radiation, ozone decomposes into an oxygen molecule and an atom. Ozone is a bactericidal agent for water disinfection. In nature, it is formed during electrical discharges, during the evaporation of water, during ultraviolet radiation, during a thunderstorm, in the mountains and in coniferous forests.

Carbon dioxide. It is formed as a result of redox processes occurring in the body of people and animals, combustion of fuel, and decay of organic substances. In the air of cities, the concentration of carbon dioxide is increased due to industrial emissions - up to 0.045%, in residential premises - up to 0.6-0.85. An adult at rest emits 22 liters of carbon dioxide per hour, and during physical work - 2-3 times more. Signs of deterioration in a person’s well-being appear only with prolonged inhalation of air containing 1-1.5% carbon dioxide, pronounced functional changes - at a concentration of 2-2.5% and pronounced symptoms (headache, general weakness, shortness of breath, palpitations, decreased performance) – at 3-4%. The hygienic importance of carbon dioxide lies in the fact that it serves as an indirect indicator of general air pollution. The carbon dioxide standard in gyms is 0.1%.

Nitrogen. An indifferent gas serves as a diluent for other gases. Increased inhalation of nitrogen can have a narcotic effect.

Carbon monoxide. Formed during incomplete combustion of organic substances. It has neither color nor smell. The concentration in the atmosphere depends on the intensity of vehicle traffic. Penetrating through the pulmonary alveoli into the blood, it forms carboxyhemoglobin, as a result of which hemoglobin loses its ability to carry oxygen. The maximum permissible average daily concentration of carbon monoxide is 1 mg/m3. Toxic doses of carbon monoxide in the air are 0.25-0.5 mg/l. With prolonged exposure, headache, fainting, palpitations.

Sulphur dioxide. It enters the atmosphere as a result of burning fuel rich in sulfur (coal). It is formed during the roasting and melting of sulfur ores and during the dyeing of fabrics. It irritates the mucous membranes of the eyes and upper respiratory tract. The sensation threshold is 0.002-0.003 mg/l. The gas has a harmful effect on vegetation, especially coniferous trees.
Mechanical air impurities come in the form of smoke, soot, soot, crushed soil particles and other solids. Air dust content depends on the nature of the soil (sand, clay, asphalt), its sanitary condition (watering, cleaning), air pollution from industrial emissions, and the sanitary condition of the premises.

Dust mechanically irritates the mucous membranes of the upper respiratory tract and eyes. Systematic inhalation of dust causes respiratory diseases. When breathing through the nose, up to 40-50% of dust is retained. Microscopic dust that remains suspended for a long time is the most unfavorable from a hygienic point of view. The electrical charge of dust enhances its ability to penetrate and linger in the lungs. Dust. containing lead, arsenic, chromium and other toxic substances, causes typical poisoning phenomena, and when penetrated not only by inhalation, but also through the skin and gastrointestinal tract. In dusty air, the intensity of solar radiation and air ionization are significantly reduced. To prevent the adverse effects of dust on the body, residential buildings are located on the windward side of air pollutants. Sanitary protection zones with a width of 50-1000 m or more are arranged between them. In residential premises, systematic wet cleaning, ventilation of premises, change of shoes and outerwear, in open areas, use non-dusting soils and watering.

Air microorganisms. Bacterial pollution of air, as well as other environmental objects (water, soil), poses an epidemiological danger. There are various microorganisms in the air: bacteria, viruses, molds, yeast cells. The most common is airborne transmission of infections: a large number of microbes enter the air and enter the respiratory tract when inhaled. healthy people. For example, during a loud conversation, and even more so when coughing and sneezing, tiny droplets are sprayed over a distance of 1-1.5 m and spread with air over 8-9 m. These droplets can be suspended for 4-5 hours, but in most cases settle in 40-60 minutes. In dust, the influenza virus and diphtheria bacilli remain viable for 120-150 days. There is a well-known relationship: the more dust there is in indoor air, the more abundant the microflora content in it.

Atmospheric air is a mixture of various gases. It contains permanent components of the atmosphere (oxygen, nitrogen, carbon dioxide), inert gases (argon, helium, neon, krypton, hydrogen, xenon, radon), small amounts of ozone, nitrous oxide, methane, iodine, water vapor, as well as in variable quantities, various impurities of natural origin and pollution resulting from production activities person.

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 a person - 15.4-16%. Reducing it in atmospheric air to 13-15% leads to disruption of physiological functions, and to 7-8% leads 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 is mainly that it is an oxygen diluent, since life is impossible in pure oxygen. When the nitrogen content increases to 93%, death occurs.

Carbon dioxide (carbon dioxide), CO2, is a physiological regulator of respiration. The content in clean air is 0.03%, in human exhalation - 3%.

A decrease in CO2 concentration in the inhaled air does not pose a danger, because its required level in the blood is maintained by regulatory mechanisms due to its release during metabolic processes.

An increase in the carbon dioxide content in the inhaled air to 0.2% causes a person to feel unwell; at 3-4% there is an excited state, headache, tinnitus, palpitations, slow pulse, and at 8% severe poisoning occurs, 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. An increase in CO2 in the atmospheric air leads to the appearance of toxic fogs in cities and the “greenhouse effect” associated with the retention of thermal radiation from the earth by carbon dioxide.

An increase in CO2 content above the established norm indicates a general deterioration in the sanitary condition of the air, since, along with carbon dioxide, other toxic substances can accumulate, the ionization regime may worsen, and dust and microbial contamination may increase.

Ozone (O3). Its main quantity is observed at the level of 20-30 km from the Earth's surface. The surface layers of the atmosphere contain a negligible amount of ozone - no more than 0.000001 mg/l. Ozone protects living organisms on the earth from the harmful effects of short-wave ultraviolet radiation and at the same time absorbs long-wave infrared radiation emanating from the Earth, protecting it from excessive cooling. Ozone has oxidizing properties, so its concentration in polluted urban air 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 atmospheric air major cities considered an indicator of its contamination.

Inert gases do not have a pronounced hygienic and physiological significance.

Human economic and production activities are a source of air pollution with various gaseous impurities and suspended particles. The increased content of harmful substances in the atmosphere and indoor air has an adverse effect on the human body. In this regard, the most important hygienic task is to standardize their permissible content in the air.

The sanitary and hygienic state of the air is usually assessed 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 a working area is a concentration that, during daily 8-hour work, but not more than 41 hours a week, during the entire working period, does not cause diseases or deviations in the health of the present and subsequent generations. The daily average and maximum one-time maximum permissible concentrations are established (valid for up to 30 minutes in the air of the working area). The maximum permissible concentration for the same substance may be different depending on the duration of its exposure to a person.

On food enterprises The main causes of air pollution with harmful substances are violations technological process and emergency situations (sewage, ventilation, etc.).

Hygienic hazards in indoor air include 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 fuel. 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 concentration of carbon monoxide in atmospheric air is 1 mg/m3, in the air of the working area - from 20 to 200 mg/m3 (depending on the duration of work).

Sulfur dioxide (S02) is the most common impurity in atmospheric air, since sulfur is contained in various types fuel. This gas has a general toxic effect and causes diseases respiratory tract. The irritating effect of the gas is detected when its concentration in the air exceeds 20 mg/m3. In atmospheric air, the average daily maximum concentration of sulfur dioxide is 0.05 mg/m3, in the air of the working area - 10 mg/m3.

Hydrogen sulfide (H2S) - usually enters the atmospheric air with waste from chemical, oil refineries and metallurgical plants, and is also formed and can pollute indoor air as a result of rotting food waste and protein products. Hydrogen sulfide has a general toxic effect and causes discomfort in humans at a concentration of 0.04-0.12 mg/m3, and a concentration of more than 1000 mg/m3 can be fatal. In atmospheric air, the average daily maximum concentration of hydrogen sulfide is 0.008 mg/m3, in the air of the working area - up to 10 mg/m3.

Ammonia (NH3) - accumulates in the air of enclosed spaces during the rotting of protein products, malfunction of refrigeration units with ammonia cooling, during sewerage failures, etc. It is toxic to the body.

Acrolein is a product of fat decomposition during heat treatment and can cause allergic diseases in industrial conditions. MPC in the working area is 0.2 mg/m3.

Polycyclic aromatic hydrocarbons (PAHs) - their connection with the development of malignant neoplasms has been noted. The most common and most active of them is 3-4-benzo(a)pyrene, which is released when fuels are burned: coal, oil, gasoline, gas. The maximum amount of 3-4-benzo(a)pyrene is released when burning coal, the minimum - when burning gas. In food processing plants, a source of PAH air pollution may be the long-term use of overheated fat. The average daily maximum concentration of cyclic aromatic hydrocarbons in atmospheric air should not exceed 0.001 mg/m3.

Mechanical impurities - dust, soil particles, smoke, ash, soot. Dust levels increase with insufficient landscaping, poor access roads, disruption of the collection and removal of production waste, as well as violation of the sanitary cleaning regime (dry or irregular wet cleaning, etc.). In addition, dustiness of premises increases with violations in the design and operation of ventilation, planning solutions (for example, with insufficient isolation of the vegetable pantry from production workshops, etc.).

The impact of dust on humans depends on the size of the dust particles and their specific gravity. The most dangerous dust particles for humans are those less than 1 micron in diameter, because... they easily penetrate the lungs and can cause chronic disease (pneumoconiosis). Dust containing admixtures of toxic chemical compounds has a toxic effect on the body.

The maximum permissible concentration for soot and soot is strictly standardized due to the content of carcinogenic hydrocarbons (PAHs): the average daily maximum concentration for soot is 0.05 mg/m3.

In high-power confectionery shops, the air may become dusty with sugar and flour dust. Flour dust in the form of aerosols can cause irritation of the respiratory tract, as well as allergic diseases. The maximum permissible concentration of flour dust in the work area should not exceed 6 mg/m3. Within these limits (2-6 mg/m3), maximum permissible concentrations of other types of plant dust containing no more than 0.2% of silicon compounds are regulated.