The quality of the air necessary to support the life processes of all living organisms on Earth is determined by the content of oxygen in it.
Consider the dependence of air quality on the percentage of oxygen in it using the example of Figure 1.

Rice. 1 Percentage of oxygen in the air

   Favorable levels of oxygen in the air

   Zone 1-2: this level of oxygen content is typical for ecologically clean areas, forests. The oxygen content in the air on the ocean can reach 21.9%

   The level of comfortable oxygen content in the air

   Zone 3-4: limited by the legally mandated minimum indoor oxygen standard (20.5%) and the "reference" fresh air (21%). For urban air, an oxygen content of 20.8% is considered normal.

   Insufficient level of oxygen in the air

   Zone 5-6: limited by the minimum allowable level of oxygen when a person can be without a breathing apparatus (18%).
A person's stay in rooms with such air is accompanied by rapid fatigue, drowsiness, decreased mental activity, and headaches.
Prolonged stay in rooms with such an atmosphere is dangerous to health.

Dangerously low oxygen levels in the air

   Zone 7 onwards: at an oxygen content of 16%, dizziness, rapid breathing are observed, 13% - loss of consciousness, 12% - irreversible changes in the functioning of the body, 7% - death.
An atmosphere unsuitable for breathing is also characterized not only by exceeding the maximum permissible concentrations of harmful substances in the air, but also by insufficient oxygen content.
Due With the different definitions given to the concept of “insufficient oxygen content”, gas rescuers very often make mistakes when describing gas rescue work. This happens, including as a result of the study of charters, instructions, standards and other documents containing an indication of the oxygen content in the atmosphere.
Consider the differences in the percentage of oxygen in the main regulatory documents.

   1.Oxygen content less than 20%.
   Gas hazardous work carried out at the oxygen content in the air of the working area less than 20%.
- Typical instructions for organizing the safe conduct of gas hazardous work (approved by the USSR Gosgortekhnadzor on February 20, 1985):
   1.5. Gas-hazardous work includes ... with insufficient oxygen content (volume fraction below 20%).
- Standard instructions for organizing the safe conduct of gas hazardous work at oil product supply enterprises TOI R-112-17-95 (approved by order of the Ministry of Fuel and Energy of the Russian Federation of July 4, 1995 N 144):
   1.3. Gas hazardous work includes ... when the oxygen content in the air is less than 20% by volume.
- National RF standard GOST R 55892-2013 "Facilities of small-scale production and consumption of liquefied natural gas. General technical requirements" (approved by order federal agency on technical regulation and metrology of December 17, 2013 N 2278-st):
   K.1 Gas-hazardous work includes work ... when the oxygen content in the air of the working area is less than 20%.

   2. Oxygen content less than 18%.
   Gas rescue work carried out with oxygen less than 18%.
- Position on gas rescue formation (approved and put into effect by the First Deputy Minister of Industry, Science and Technology Svinarenko A.G. on 05.06.2003; approved by: Federal Mining and Industrial Supervision Russian Federation May 16, 2003 N AC 04-35/373).
   3. Gas rescue operations ... in conditions of reducing the oxygen content in the atmosphere to a level of less than 18 vol.% ...
- Management on the organization and conduct of emergency rescue operations at the enterprises of the chemical complex (approved by the UAC No. 5/6 protocol No. 2 of 07/11/2015).
   2. Gas rescue operations ... in conditions of insufficient (less than 18%) oxygen content ...
- GOST R 22.9.02-95 Safety in emergency situations. Modes of activity of rescuers using personal protective equipment in the aftermath of accidents at chemically hazardous facilities. General requirements (adopted as an interstate standard GOST 22.9.02-97)
   6.5 At high concentrations of OHV and insufficient oxygen content (less than 18%) in the focus of chemical contamination, use only insulating respiratory protective equipment.

   3. Oxygen content less than 17%.
   The use of filters is prohibited. PPE with oxygen content less than 17%.
- GOST R 12.4.233-2012 (EN 132:1998) System of labor safety standards. Personal respiratory protection. Terms, definitions and designations (approved and put into effect by order of the Federal Agency for Technical Regulation and Metrology dated November 29, 2012 N 1824-st)
   2.87…oxygen-deficient atmosphere: Ambient air containing less than 17% oxygen by volume in which PPE cannot be used.
- Interstate standard GOST 12.4.299-2015 System of labor safety standards. Personal respiratory protection. Recommendations for the selection, application and maintenance (put into effect by order of the Federal Agency for Technical Regulation and Metrology dated June 24, 2015 N 792-st)
   B.2.1 Oxygen deficiency. If the analysis of environmental conditions indicates the presence or possibility of oxygen deficiency (volume fraction less than 17%), then filter-type RPE is not used ...
- Solution Commission of the Customs Union dated December 9, 2011 N 878 On the adoption of the technical regulation of the Customs Union "On the safety of personal protective equipment"
   7) ... it is not allowed to use filtering means of personal respiratory protection when the oxygen content in the inhaled air is less than 17 percent
- Interstate standard GOST 12.4.041-2001 System of labor safety standards. Means of individual protection of respiratory organs filtering. General technical requirements
   1 ... filtering means of personal respiratory protection designed to protect against aerosols, gases and vapors harmful to health and their combinations in the ambient air, provided that the oxygen content in it is at least 17 vol. %.

The lower layers of the atmosphere are made up 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. Near 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% falls almost entirely on 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

The composition of dry atmospheric air near the Earth's surface

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

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

Water vapor continuously enters the atmosphere by evaporation from water surfaces, from moist soil and by plant transpiration, while in different places and at different times it enters in different quantities. It spreads upward from the earth's surface, and is carried by air currents from one place on the Earth to another.

Saturation may occur in the atmosphere. In this state, water vapor is contained in the air in an amount that is the 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 drops. When this state is reached, then with a further decrease in temperature, part of the water vapor becomes redundant and condenses changes to a liquid or solid state. Water droplets and ice crystals of clouds and fogs appear in the air. Clouds can evaporate again; in other cases, droplets and crystals of clouds, becoming larger, can fall on 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.

The most important weather processes and climate features are associated with water vapor in the air and with its transitions from a gaseous state to a liquid and solid state. 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, he himself emits infrared radiation, most of which goes to the earth's surface. This reduces the nighttime cooling of the earth's surface and thus also the lower layers of the air.

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 essential for physiological processes.

Water vapor, like any gas, has elasticity (pressure). Water vapor pressure e 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° saturation elasticity is 6.1 mb . For every 10° of temperature, the saturation elasticity approximately doubles.

If the air contains less water vapor than is needed to saturate it at a given temperature, it can be determined how close the air is to saturation. To do this, calculate relative humidity. This is the name of 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 elasticity is 23.4 mb. If the actual vapor pressure in the air is 11.7 mb, then the relative humidity of the air is

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

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

The chemical composition of the air

Air has such chemical composition: nitrogen-78.08%, oxygen-20.94%, inert gases-0.94%, carbon dioxide-0.04%. These indicators in the surface layer can fluctuate within insignificant limits. Man basically needs oxygen, without which he cannot live, like other living organisms. But now it has been studied and proven that other constituents of the air are also of great importance.

Oxygen is a colorless and odorless gas, highly soluble in water. A person inhales approximately 2722 liters (25 kg) of oxygen per day at rest. Exhaled air contains about 16% oxygen. The nature of the intensity of oxidative processes in the body depends on the amount of oxygen consumed.

Nitrogen is a colorless and odorless gas, inactive, its concentration in the exhaled air almost does not change. It plays an important physiological role in creating atmospheric pressure, which is vital, and, together with inert gases, dilutes oxygen. With plant foods (especially legumes), nitrogen in a bound form enters the body of animals and participates in the formation of animal proteins, and, accordingly, the proteins of the human body.

Carbon dioxide is a colorless gas with a sour taste and a peculiar smell, highly soluble in water. The air exhaled from the lungs contains up to 4.7%. An increase in the carbon dioxide content of 3% in the inhaled air negatively affects the state of the body, there are sensations of compression of the head and headache, blood pressure rises, the pulse slows down, tinnitus appears, and mental arousal can be observed. With an increase in the concentration of carbon dioxide up to 10% in the inhaled air, loss of consciousness occurs, and then respiratory arrest may occur. Large concentrations quickly lead to paralysis of the brain centers and death.

The main chemical impurities that pollute the atmosphere are the following.

carbon monoxide(CO) - a colorless, odorless gas, the so-called "carbon monoxide". It is formed as a result of incomplete combustion of fossil fuels (coal, gas, oil) in conditions of lack of oxygen at low temperatures.

Carbon dioxide(CO 2), or carbon dioxide - a colorless gas with a sour smell and taste, a product of the complete oxidation of carbon. It is one of the greenhouse gases.

Sulfur dioxide(SO 2) or sulfur dioxide is a colorless gas with a pungent odor. It is formed during the combustion of sulfur-containing fossil fuels, mainly coal, as well as during the processing of sulfur ores. It is involved in the formation of acid rain. Prolonged exposure to sulfur dioxide on a person leads to circulatory disorders and respiratory arrest.

nitrogen oxides(oxide and nitrogen dioxide). Formed during all combustion processes mostly in the form of nitrogen oxide. Nitric oxide quickly oxidizes to dioxide, which is a red-white gas with an unpleasant odor that strongly affects human mucous membranes. The higher the combustion temperature, the more intense the formation of nitrogen oxides.

Ozone- a gas with a characteristic odor, a stronger oxidizing agent than oxygen. It is considered one of the most toxic of all common air pollutants. In the lower atmospheric layer, ozone is formed as a result of photo chemical processes with the participation of nitrogen dioxide and volatile organic compounds (VOCs).

hydrocarbons- chemical compounds of carbon and hydrogen. These include thousands of different air pollutants found in unburned gasoline, dry cleaning fluids, industrial solvents, and more. Many hydrocarbons are dangerous in and of themselves. For example, benzene, one of the components of gasoline, can cause leukemia, and hexane can cause severe damage to the human nervous system. Butadiene is a strong carcinogen.

Lead- a silver-gray metal, toxic in any known form. Widely used in the production of solder, paint, ammunition, printing alloy, etc. Lead and its compounds, getting into the human body, reduce the activity of enzymes and disrupt the metabolism, in addition, they have the ability to accumulate in the human body. Lead compounds pose a particular threat to children, disrupting their mental development, growth, hearing, the child's speech, and his ability to concentrate.

Freons- a group of halogen-containing substances synthesized by man. Freons, which are chlorinated and fluorinated carbons (CFCs), as inexpensive and non-toxic gases, are widely used as refrigerants in refrigerators and air conditioners, foaming agents, in gas fire extinguishing installations, and the working fluid of aerosol packages (varnishes, deodorants).

industrial dust Depending on the mechanism of their formation, they are divided into the following classes:

mechanical dust - is formed as a result of grinding the product during the technological process,

sublimates - are formed as a result of volumetric condensation of vapors of substances during cooling of a gas passed through a process apparatus, installation or unit,

fly ash - the non-combustible fuel residue contained in the flue gas in suspension, is formed from its mineral impurities during combustion,

industrial soot - a solid highly dispersed carbon, which is part of an industrial emission, is formed during incomplete combustion or thermal decomposition of hydrocarbons.

The main parameter characterizing suspended particles is their size, which varies in a wide range - from 0.1 to 850 microns. The most dangerous particles are from 0.5 to 5 microns, since they do not settle in the respiratory tract and it is them that a person inhales.

Dioxins belong to the class of polychlorinated polycyclic compounds. Under this name, more than 200 substances are combined - dibenzodioxins and dibenzofurans. The main element of dioxins is chlorine, which in some cases can be replaced by bromine, in addition, dioxins contain oxygen, carbon and hydrogen.

Atmospheric air acts as a kind of mediator of pollution of all other objects of nature, contributing to the spread of large masses of pollution over considerable distances. Airborne industrial emissions (impurities) pollute the oceans, acidify soil and water, change the climate and destroy the ozone layer.

We all know very well that without air not a single one can live on earth. Living being. Air is vital for all of us. Everyone from children to adults knows that it is impossible to survive without air, but not everyone knows what air is and what it consists of. So, air is a mixture of gases that cannot be seen or touched, but we all know perfectly well that it is around us, although we practically do not notice it. To conduct research of a different nature, including, it is possible in our laboratory.

We can feel the air only when we feel a strong wind or we are near the fan. What does air consist of, and it consists of nitrogen and oxygen, and only a small part of argon, water, hydrogen and carbon dioxide. If we consider the composition of air as a percentage, then nitrogen is 78.08 percent, oxygen 20.94%, argon 0.93 percent, carbon dioxide 0.04 percent, neon 1.82 * 10-3 percent, helium 4.6 * 10-4 percent, methane 1.7 * 10-4 percent, krypton 1.14*10-4 percent, hydrogen 5*10-5 percent, xenon 8.7*10-6 percent, nitrous oxide 5*10-5 percent.

The oxygen content in the air is very high because it is oxygen that is necessary for life. human body. Oxygen, which is observed in the air during breathing, enters the cells of the human body, and participates in the oxidation process, as a result of which energy is released, which is needed for life. Also, oxygen, which is in the air, is also required for burning fuel, which produces heat, as well as for obtaining mechanical energy in internal combustion engines.

Inert gases are also extracted from the air during liquefaction. How much oxygen is in the air, if you look at the percentage, then oxygen and nitrogen in the air is 98 percent. Knowing the answer to this question, another one arises, which gaseous substances are still part of the air.

So, in 1754, a scientist named Joseph Black confirmed that the air consists of a mixture of gases, and not a homogeneous substance, as previously thought. The composition of air on earth includes methane, argon, carbon dioxide, helium, krypton, hydrogen, neon, xenon. It is worth noting that the percentage of air can vary slightly depending on where people live.

Unfortunately, in major cities the proportion of carbon dioxide as a percentage will be higher than, for example, in villages or forests. The question arises how many percent of oxygen is in the air in the mountains. The answer is simple, oxygen is much heavier than nitrogen, so it will be much less in the air in the mountains, this is because the density of oxygen decreases with height.

The rate of oxygen in the air

So, with regard to the ratio of oxygen in the air, there are certain standards, for example, for the working area. In order for a person to be able to fully work, the norm of oxygen in the air is from 19 to 23 percent. When operating equipment in enterprises, it is imperative to monitor the tightness of the devices, as well as various machines. If, when testing the air in a room where people work, the oxygen indicator is below 19 percent, then it is imperative to leave the room and turn on emergency ventilation. You can control the level of oxygen in the air at the workplace by inviting the EcoTestExpress laboratory and researching.

Let's now define what oxygen is.

Oxygen is chemical element periodic table elements of Mendeleev, oxygen has no smell, no taste, no color. Oxygen in the air is essential for human respiration, as well as for combustion, because it is no secret to anyone that if there is no air, then no materials will burn. The composition of oxygen includes a mixture of three stable nuclides, the mass numbers of which are 16, 17 and 18.

So, oxygen is the most common element on earth, with regard to the percentage of oxygen, the largest percentage is in silicates, which is about 47.4 percent of the mass of the solid earth's crust. Also in marine and fresh waters The entire earth contains a huge amount of oxygen, namely 88.8 percent, as for the amount of oxygen in the air, it is only 20.95 percent. It should also be noted that oxygen is part of more than 1500 compounds in the earth's crust.

As for the production of oxygen, it is obtained by separating air at low temperatures. This process occurs as follows, at the beginning they compress the air with the help of a compressor, while compressing the air, it begins to heat up. The compressed air is allowed to cool to room temperature, and after cooling, it is allowed to expand freely.

When expansion occurs, the gas temperature begins to drop sharply, after the air has cooled, its temperature can be several tens of degrees lower than room temperature, such air is again subjected to compression and the released heat is taken away. After several stages of air compression and cooling, a number of procedures are performed as a result of which pure oxygen is separated without any impurities.

And here another question arises which is heavier oxygen or carbon dioxide. The answer is simply of course carbon dioxide will be heavier than oxygen. The density of carbon dioxide is 1.97 kg/m3, while the density of oxygen is 1.43 kg/m3. As for carbon dioxide, as it turns out, it plays one of the main roles in the life of all life on earth, and also has an impact on the carbon cycle in nature. It has been proven that carbon dioxide is involved in the regulation of respiration, as well as blood circulation.

What is carbon dioxide?

Now let's define in more detail what carbon dioxide is, and also denote the composition of carbon dioxide. So, carbon dioxide in other words is carbon dioxide, it is a colorless gas with a slightly sour smell and taste. As for the air, the concentration of carbon dioxide in it is 0.038 percent. physical properties carbon dioxide is that it does not exist in a liquid state under normal atmospheric pressure and goes directly from the solid to the gaseous state.

Carbon dioxide in the solid state is also called dry ice. To date, carbon dioxide is a participant global warming. Carbon dioxide is produced by burning various substances. It should be noted that in the industrial production of carbon dioxide, it is pumped into cylinders. Carbon dioxide pumped into cylinders is used as fire extinguishers, as well as in the production of soda water, and is also used in pneumatic weapons. And also in the food industry as a preservative.

Composition of inhaled and exhaled air

Now let's analyze the composition of the inhaled and exhaled air. First, let's define what breathing is. Breathing is a complex continuous process by which the gas composition of the blood is constantly updated. The composition of the air we breathe is 20.94 percent oxygen, 0.03 percent carbon dioxide, and 79.03 percent nitrogen. But the composition of the exhaled air is already only 16.3 percent oxygen, as much as 4 percent carbon dioxide and 79.7 percent nitrogen.

It can be seen that the inhaled air differs from the exhaled by the content of oxygen, as well as the amount of carbon dioxide. These are the substances that make up the air we breathe and exhale. Thus, our body is saturated with oxygen and releases all unnecessary carbon dioxide to the outside.

Dry oxygen improves the electrical and protective properties of the films due to the absence of water, as well as their compaction and reduction of the space charge. Also, dry oxygen under normal conditions cannot react with gold, copper or silver. To spend chemical analysis air or other laboratory research, including, is possible in our laboratory "EkoTestEkspress".

Air is the atmosphere of the planet on which we live. And we always have the question of what is part of the air, the answer is simply a set of gases, as it has already been described above, which gases and in what proportion are in the air. As for the content of gases in the air, everything is easy and simple here, the percentage ratio for almost all areas of our planet is the same.

Composition and properties of air

Air consists not only of a mixture of gases, but also of various aerosols and vapors. The percentage composition of air is the ratio of nitrogen to oxygen and other gases in the air. So, how much oxygen is in the air, the simple answer is only 20 percent. The component composition of the gas, as for nitrogen, it contains the lion's share of all air, and it is worth noting that at elevated pressure, nitrogen begins to have narcotic properties.

This is of no small importance, because when divers work, they often have to work at depths under enormous pressure. A lot has already been said about oxygen, because it is of great importance for human life on our planet. It is worth noting that the inhalation of air with increased oxygen by a person in a short period does not adversely affect the person himself.

But if a person breathes air with increased level oxygen for a long time, it will lead to pathological changes in the body. Another main component of the air, about which much has already been said, is carbon dioxide, as it turns out, a person cannot live without it as well as without oxygen.

If there was no air on earth, then not one living organism could live on our planet, much less function somehow. Unfortunately, in modern world a huge number of industrial facilities that pollute our air, in Lately increasingly calling for what needs to be protected environment and keep the air clean. Therefore, frequent air measurements should be taken to determine how clean it is. If it seems to you that the air in your room is not clean enough and this is to blame external factors you can always contact the EcoTestExpress laboratory, which will conduct all the necessary analyzes (, research) and give a conclusion about the purity of the air you breathe.

That part of the atmosphere, which is adjacent to the Earth and which, accordingly, a person breathes, is called the troposphere. The troposphere has a height of nine to eleven kilometers and is a mechanical mixture of various gases.

The composition of the air is not constant. Depending on the geographical location, terrain, weather conditions, air can have a different composition and different properties. The air can be gassed or discharged, fresh or heavy - all this means that it contains certain impurities.

Nitrogen - 78.9 percent;

Oxygen - 20.95 percent;

Carbon dioxide - 0.3 percent.

In addition, other gases are present in the atmosphere (helium, argon, neon, xenon, krypton, hydrogen, radon, ozone), as well as their sum is slightly less than one percent.

It is also worth pointing out the presence in the air of some permanent impurities of natural origin, in particular, some gaseous products that are formed as a result of both biological and chemical processes. Ammonia deserves special mention among them (the composition of air away from populated areas includes about three to five thousandths of a milligram per cubic meter), methane (its level is on average two ten thousandths of a milligram per cubic meter), nitrogen oxides (in the atmosphere, their concentration reaches approximately fifteen ten thousandths of a milligram per cubic meter), hydrogen sulfide and other gaseous products.

In addition to vapor and gaseous impurities, the chemical composition of the air usually includes dust of cosmic origin, which falls on the Earth's surface in the amount of seven hundred thousandths of a ton per square kilometer during the year, as well as dust particles that come from volcanic eruptions.

However, it changes to the greatest extent (and not in better side) the composition of the air and the so-called ground (vegetable, soil) dust and smoke pollute the troposphere forest fires. Especially a lot of such dust in the continental air masses originating in the deserts of Central Asia and Africa. That is why we can confidently say that perfectly clean air environment simply does not exist, and it is a concept that exists only theoretically.

The composition of the air tends to change constantly, and its natural changes usually play a rather small role, especially in comparison with the possible consequences of its artificial disturbances. Such violations are mainly associated with the production activities of mankind, the use of devices for consumer services, as well as vehicles. These violations can lead, among other things, to air denaturation, that is, to pronounced differences in its composition and properties from the corresponding indicators of the atmosphere.

These and many other types human activity led to the fact that the main composition of the air began to undergo slow and insignificant, but nevertheless absolutely irreversible changes. For example, scientists have calculated that over the past fifty years, mankind has used about the same amount of oxygen as over the previous million years, and in percentage terms - two-tenths of a percent of its total supply in the atmosphere. At the same time, the release into the air increases accordingly. This release, according to the latest data, has reached almost four hundred billion tons over the past hundred years.

Thus, the composition of the air is changing for the worse, and it is difficult to imagine what it will become in a few decades.