Given in Table. 1.1 The composition of atmospheric air undergoes various changes in enclosed spaces. Firstly, the percentage of certain essential components changes, and, secondly, additional impurities appear that are not characteristic of pure air. In this paragraph, we will discuss changes in the gas composition and its permissible deviations from normal.

The most important gases for human life are oxygen and carbon dioxide, which are involved in the gas exchange of a person with the environment. This gas exchange takes place mainly in the human lungs during respiration. Gas exchange occurring through the surface of the skin is about 100 times less than through the lungs, since the surface of the body of an adult is approximately 1.75 m2, and the surface of the alveoli of the lungs is about 200 m2. The process of respiration is accompanied by the formation of heat in the human body in an amount of 4.69 to 5.047 (on average 4.879) kcal per 1 liter of absorbed oxygen (passed into carbon dioxide). It should be noted that only a small part of the oxygen contained in the inhaled air (approximately 20%) is absorbed. So, if in the atmospheric air there is approximately 21% of oxygen, then in the air exhaled by a person it will be about 17%. Typically, the amount of carbon dioxide exhaled is less than the amount of oxygen taken in. The ratio of the amount of carbon dioxide emitted by a person and the oxygen absorbed is called the respiratory coefficient (RC), which usually ranges from 0.71 to 1. However, if a person is in a state of strong excitement or performs very hard work, the ROC can be even greater than one.

The amount of oxygen necessary for a person to maintain normal life activity mainly depends on the intensity of the work performed by him and is determined by the degree of nervous and muscular tension. Assimilation of oxygen by the blood occurs best at a partial pressure of about 160 mm Hg. Art., which at an atmospheric pressure of 760 mm Hg. Art. corresponds to the normal percentage of oxygen in the atmospheric air, i.e. 21%.

Due to the ability of the human body to adapt, normal breathing can be observed even with smaller amounts of oxygen.

If the reduction in the oxygen content in the air occurs due to inert gases (for example, nitrogen), then a significant decrease in the amount of oxygen is possible - up to 12%.

However, in enclosed spaces, a decrease in the oxygen content is accompanied not by an increase in the concentration of inert gases, but by the accumulation of carbon dioxide. Under these conditions, the maximum allowable minimum oxygen content in the air should be much higher. Usually, the oxygen content equal to 17% by volume is taken as the norm for this concentration. Generally speaking, indoors, the percentage of oxygen never drops to this level, since the concentration of carbon dioxide reaches the limit value much earlier. Therefore, it is practically more important to establish the maximum allowable norms for the content of not oxygen, but carbon dioxide in enclosed spaces.

Carbon dioxide CO2 is a colorless gas with a slight sour taste and smell; it is 1.52 times heavier than air, slightly poisonous. The accumulation of carbon dioxide in indoor air leads to headaches, dizziness, weakness, loss of sensation and even loss of consciousness.

It is believed that in atmospheric air the amount of carbon dioxide is 0.03% by volume. This is true for rural areas. In the air of large industrial centers, its content is usually higher. For calculations, a concentration of 0.04% is taken. The air exhaled by a person contains about 4% carbon dioxide.

Without any harmful consequences for the human body, concentrations of carbon dioxide much higher than 0.04% can be tolerated in indoor air.

The value of the maximum allowable concentration of carbon dioxide depends on the length of stay of people in a particular enclosed space and on their occupation. For example, for sealed shelters, when healthy people are placed in them for a period of not more than 8 hours, a norm of 2% can be taken as the maximum allowable concentration of CO2. With a short stay of people, this rate can be increased. The ability of a person to stay in an environment with high concentrations of carbon dioxide is due to the ability of the human body to adapt to various conditions. At a concentration of CO2 higher than 1%, a person begins to inhale significantly more air. Thus, at a CO2 concentration of 3%, respiration doubles even at rest, which in itself does not cause noticeable negative consequences during a relatively short stay in such air of a person. If a person stays in a room with a CO2 concentration of 3% for a sufficiently long time (3 or more days), he is threatened with loss of consciousness.

With a long stay of people in sealed rooms and when people perform one or another work, the value of the maximum allowable concentration of carbon dioxide should be significantly less than 2%. It can fluctuate from 0.1 to 1%. A carbon dioxide content of 0.1% can also be considered acceptable for ordinary non-pressurized premises of buildings and structures for various purposes. A lower concentration of carbon dioxide (of the order of 0.07-0.08) should be prescribed only for the premises of medical and children's institutions.

As will be clear from the following, the requirements for the content of carbon dioxide in the air of the premises of ground buildings are usually easily met if the sources of its release are people. The question is different when carbon dioxide accumulates in industrial premises as a result of certain technological processes occurring, for example, in yeast, brewing, hydrolysis shops. In this case, 0.5% is taken as the maximum allowable concentration of carbon dioxide.

Unlike the hot and cold planets in our solar system, there are conditions on planet Earth that allow life in some form. One of the main conditions is the composition of the atmosphere, which gives all living things the opportunity to breathe freely and protects from the deadly radiation that reigns in space.

What is the atmosphere made of?

The Earth's atmosphere is made up of many gases. Basically which occupies 77%. Gas, without which life on Earth is unthinkable, occupies a much smaller volume, the oxygen content in the air is 21% of the total volume of the atmosphere. The last 2% is a mixture of various gases, including argon, helium, neon, krypton and others.

The Earth's atmosphere rises to a height of 8,000 km. Breathable air exists only in the lower layer of the atmosphere, in the troposphere, which reaches 8 km at the poles, upwards, and 16 km above the equator. As altitude increases, the air becomes thinner and the more oxygen is depleted. To consider what oxygen content in the air is at different heights, we will give an example. At the peak of Everest (altitude 8848 m), the air holds this gas 3 times less than above sea level. Therefore, the conquerors of high mountain peaks - climbers - can climb to its top only in oxygen masks.

Oxygen is the main condition for survival on the planet

At the beginning of the existence of the Earth, the air that surrounded it did not have this gas in its composition. This was quite suitable for the life of the simplest - single-celled molecules that floated in the ocean. They didn't need oxygen. The process began about 2 million years ago, when the first living organisms, as a result of the reaction of photosynthesis, began to release small doses of this gas obtained as a result of chemical reactions, first into the ocean, then into the atmosphere. Life evolved on the planet and took on a variety of forms, most of which have not survived to our times. Some organisms eventually adapted to life with the new gas.

They learned to use its power safely inside the cell, where it acted as a power plant, in order to extract energy from food. This way of using oxygen is called breathing, and we do it every second. It was breathing that made it possible for the emergence of more complex organisms and people. Over millions of years, the oxygen content in the air has soared to its current level - about 21%. The accumulation of this gas in the atmosphere contributed to the creation of the ozone layer at a height of 8-30 km from the earth's surface. At the same time, the planet received protection from the harmful effects of ultraviolet rays. The further evolution of life forms on water and on land increased rapidly as a result of increased photosynthesis.

anaerobic life

Although some organisms have adapted to the rising levels of the gas being released, many of the simplest life forms that existed on Earth have disappeared. Other organisms survived by hiding from oxygen. Some of them today live in the roots of legumes, using nitrogen from the air to build amino acids for plants. The deadly organism botulism is another "refugee" from oxygen. He quietly survives in vacuum packaging with canned foods.

What oxygen level is optimal for life

Prematurely born babies, whose lungs are not yet fully opened for breathing, fall into special incubators. In them, the oxygen content in the air is higher by volume, and instead of the usual 21%, its level of 30-40% is set here. Toddlers with severe breathing problems are surrounded by air with 100% oxygen levels to prevent damage to the child's brain. Being in such circumstances improves the oxygen regime of tissues that are in a state of hypoxia, and normalizes their vital functions. But its excessive amount in the air is just as dangerous as the lack of it. Too much oxygen in a child's blood can damage the blood vessels in the eyes and cause vision loss. This shows the duality of the properties of the gas. We must breathe it in order to live, but its excess can sometimes become a poison for the body.

Oxidation process

When oxygen combines with hydrogen or carbon, a reaction called oxidation takes place. This process causes the organic molecules that are the basis of life to decay. In the human body, oxidation proceeds as follows. Red blood cells collect oxygen from the lungs and carry it throughout the body. There is a process of destruction of the molecules of the food that we eat. This process releases energy, water and carbon dioxide. The latter is excreted by the blood cells back into the lungs, and we exhale it into the air. A person can suffocate if they are prevented from breathing for more than 5 minutes.

Breath

Consider the oxygen content in the air we breathe. Atmospheric air that enters the lungs from the outside when inhaled is called inhaled, and the air that goes out through the respiratory system when exhaled is called exhaled.

It is a mixture of air that filled the alveoli with that which is in the respiratory tract. The chemical composition of the air that a healthy person inhales and exhales under natural conditions practically does not change and is expressed in such numbers.

Oxygen is the main constituent of air for life. Changes in the amount of this gas in the atmosphere are small. If by the sea the oxygen content in the air contains up to 20.99%, then even in the very polluted air of industrial cities, its level does not fall below 20.5%. Such changes do not reveal effects on the human body. Physiological disorders appear when the percentage of oxygen in the air drops to 16-17%. At the same time, there is a clear one that leads to a sharp drop in vital activity, and with an oxygen content in the air of 7-8%, a lethal outcome is possible.

Atmosphere in different eras

The composition of the atmosphere has always influenced evolution. At different geological times, due to natural disasters, rises or falls in the level of oxygen were observed, and this entailed a change in the biosystem. Approximately 300 million years ago, its content in the atmosphere rose to 35%, while the planet was inhabited by gigantic insects. The largest extinction of living beings in the history of the Earth happened about 250 million years ago. During it, more than 90% of the inhabitants of the ocean and 75% of the inhabitants of the land died. One version of the mass extinction says that the low oxygen content in the air was to blame. The amount of this gas has dropped to 12% and it is in the lower atmosphere up to a height of 5300 meters. In our era, the oxygen content in the atmospheric air reaches 20.9%, which is 0.7% lower than 800 thousand years ago. These figures are confirmed by scientists at Princeton University who examined samples of the Greenland and Atlantic ice that formed at that time. The frozen water saved the air bubbles, and this fact helps to calculate the level of oxygen in the atmosphere.

What is its level in the air

Active absorption of it from the atmosphere can be caused by the movement of glaciers. As they move away, they reveal vast areas of organic layers that consume oxygen. Another reason may be the cooling of the waters of the oceans: its bacteria absorb oxygen more actively at low temperatures. The researchers argue that the industrial leap and with it the burning of a huge amount of fuel does not have a special impact. The world's oceans have been cooling for 15 million years, and the amount of vital matter in the atmosphere has decreased regardless of human impact. Probably, some natural processes are taking place on Earth, leading to the fact that the consumption of oxygen becomes higher than its production.

Human impact on the composition of the atmosphere

Let's talk about the influence of man on the composition of the air. The level that we have today is ideal for living beings, the oxygen content in the air is 21%. The balance of carbon dioxide and other gases is determined by the life cycle in nature: animals exhale carbon dioxide, plants use it and release oxygen.

But there is no guarantee that this level will always be constant. The amount of carbon dioxide released into the atmosphere is increasing. This is due to the use of fuel by mankind. And it, as you know, was formed from fossils of organic origin and carbon dioxide enters the air. Meanwhile, the largest plants on our planet, trees, are being destroyed at an increasing rate. Kilometers of forest disappear in a minute. This means that part of the oxygen in the air is gradually falling and scientists are already sounding the alarm. The earth's atmosphere is not a limitless pantry and oxygen does not enter it from the outside. It has been developed all the time along with the development of the Earth. It must be constantly remembered that this gas is produced by vegetation in the process of photosynthesis due to the consumption of carbon dioxide. And any significant reduction in vegetation in the form of deforestation inevitably reduces the ingress of oxygen into the atmosphere, thereby disturbing its balance.

The composition of the air on earth is one of the reasons for our life. Without air, a person will live only three minutes, and after 10 clinical death will occur.

While we breathe, we live. No other planet in the solar system has such a close relationship between chemistry and biology. Our world is unique.

Depending on the territory, the volume of the main component of the vital gas is from 16 to 20 percent - this is oxygen, the formula of which is O 2. Its variation is felt in space as “freshness” after a thunderstorm - this is ozone O 3.

From this article you will learn all the secrets of the air shell of the earth. What will happen to the world without one component? What harm can it do? How will a slight deterioration in the atmosphere affect life?

What is air

The ancient Greeks used two words as a definition for air: calamus, which meant the lower layers of the atmosphere (Dim), and ether meant the bright upper layers of the atmosphere (transcendental space).

In alchemy, the symbol for air is a triangle divided in two by a horizontal line.

In the modern world, such a definition would suit him - a gas mixture that surrounds the planet, which protects against the penetration of solar radiation and large doses of ultraviolet radiation.

Over a multimillion-year period of development, the planet has transformed gaseous substances and created a unique protective shield, which is almost impossible to see. Their mass fraction is incommensurably small for space.

Nothing else has an impact on the formation of the world. If we remember that part of the air masses is oxygen, then what will happen on earth without it? Buildings and structures will collapse.

Metal bridges and other structures that fascinate millions of tourists will turn into a single lump due to the small number of oxygen molecules (in this situation, close to zero). The life of all living organisms on the planet will worsen, and some will lead to death.

Seas and oceans, evaporating in the form of hydrogen, will disappear. And when the planet becomes like the moon, a radiation fire will reign, burning out the remains of the flora, because without oxygen the temperature will increase very much, but without the atmosphere there will be no protection from the sun.

What is air made of

Almost the entire earth's atmosphere consists of only five gases: nitrogen, oxygen, water vapor, argon and carbon dioxide.

Other mixtures are also present in it, but for the sake of clarity of presentation, the chemical composition of water vapor will not be considered. It is worth mentioning that in the air mass it occupies no more than five percent.

Composition of air in percent

Ideally, the air collected in a jar consists of:

• 78 percent from nitrogen;
• 16 - 20 percent oxygen;
• 1 percent argon;
• three hundredths of a percent of carbon dioxide;
• one thousandth of a percent of neon;
• 0.0002 percent methane.

The smaller components are:

• helium - 0.000524%;
• krypton - 0.000114%;
• hydrogen - H2 0.00005%;
• xenon - 0.0000087%;
• ozone O 3 - 0.000007%;
• nitrogen dioxide - 0.000002%;
• iodine - 0.000001%;
• carbon monoxide;
• ammonia.

Composition of inhaled and exhaled air

Breathing takes precedence over other human needs. From the school course, everyone knows that a person inhales oxygen and exhales carbon dioxide. Although in life, in addition to pure O 2, other substances are present in the air.

Inhale - exhale. A similar cycle is repeated about 22,000 times a day, during which oxygen is consumed, which maintains the vitality of the human body. The problem is that delicate lung tissue is attacked by air pollution, cleaning solutions, fibers, fumes and dust.

The first half of the article talked about reducing oxygen, but what will happen with an increase. Doubling the concentration of the main gas would lead to a reduction in fuel consumption in cars.

By inhaling more oxygen, a person would become much more psychologically positive. However, for some insects, a favorable climate would allow them to increase in size. There are a number of theories that predict this. It seems that no one would like to meet a spider the size of a dog, and one can only fantasize about the growth of large representatives.

By inhaling less heavy metals, humanity could defeat a number of complex diseases, but such a project will require a lot of effort. There is a whole program aimed at creating a practical paradise on earth: in every house, room, city or country. Its goal is to make the atmosphere cleaner, to save people from dangerous work in mines and metallurgy. A place where jobs would be occupied by masters of their craft.

It is important that it is possible to inhale clean, untouched by industry air, but this requires political, or better, world will. In the meantime, people are busy looking for money and cheap (dirty) technologies, only city smog remains to be inhaled. How long this will last is unknown.

A map will allow you to visually assess the atmospheric air of the capital of our country, which is inhaled by more than a dozen people.

Hygienic value of atmospheric air

Officially, air pollution can be defined as the content of harmful substances in the air or particles or microscopic biological molecules that pose a health hazard to living organisms: humans, animals or plants.

The level of air pollution in a particular location depends mainly on the source or sources of pollution. This includes:

• vehicle exhaust gases;
• coal power plants;
• industrial plants and other sources of pollution.

All of the above spews various types of hazardous substances and toxins into the air, exceeding the norm by tens, and sometimes hundreds of times. In combination with natural sources - volcanoes, geysers, etc. - a deadly cocktail of poisonous air masses is created, which is commonly called "smog".

The evidence of each person's guilt is clear. Our personal choices and industry can have a detrimental effect on much-needed gas. For a century of technological breakthrough, nature has managed to suffer, which means revenge is inevitable.

By increasing emissions, humanity is approaching the abyss, from which there is no return and cannot be. Before it's too late, at least something should be corrected. It has been proven that alternative industrial technologies can help clean the air in Moscow, St. Petersburg, Tokyo, Berlin and any other major city.

Here are some solutions:

1. Replace gasoline with electricity in cars, and the sky above the city will become a little more beautiful.
2. Remove coal stations from cities, let them go down in the history of the country, start using the energy of the sun, water, and wind. Then, after the rain, soot will not fly from the chimney of the next plant, but there will be only the smell of “freshness”.
3. Plant a tree in the park. If thousands do this, then asthmatics and depressed people will stop visiting hospitals in search of a unique recipe from the lips of a psychologist.

Let's make a reservation right away, nitrogen in the air occupies a large part, however, the chemical composition of the remaining share is very interesting and diverse. In short, the list of main elements is as follows.

However, we will also give some explanations on the functions of these chemical elements.

1. Nitrogen

The content of nitrogen in the air is 78% by volume and 75% by mass, that is, this element dominates in the atmosphere, has the title of one of the most common on Earth, and, in addition, is found outside the human habitation zone - on Uranus, Neptune and in interstellar spaces. So, how much nitrogen is in the air, we have already figured out, the question remains about its function. Nitrogen is necessary for the existence of living beings, it is part of:

• proteins;
• amino acids;
• nucleic acids;
• chlorophyll;
• hemoglobin, etc.

On average, about 2% of a living cell is just nitrogen atoms, which explains why there is so much nitrogen in the air as a percentage of volume and mass.
Nitrogen is also one of the inert gases extracted from atmospheric air. Ammonia is synthesized from it, used for cooling and for other purposes.

2. Oxygen

The oxygen content in the air is one of the most popular questions. Keeping the intrigue, let's digress to one funny fact: oxygen was discovered twice - in 1771 and 1774, however, due to the difference in the publications of the discovery, the credit for the discovery of the element went to the English chemist Joseph Priestley, who actually isolated oxygen second. So, the proportion of oxygen in the air fluctuates around 21% by volume and 23% by mass. Together with nitrogen, these two gases form 99% of the earth's air. However, the percentage of oxygen in the air is less than nitrogen, and yet we do not experience breathing problems. The fact is that the amount of oxygen in the air is optimally calculated specifically for normal breathing, in its pure form this gas acts on the body like a poison, leads to difficulties in the functioning of the nervous system, respiratory failure and blood circulation. At the same time, the lack of oxygen also negatively affects health, causing oxygen starvation and all the unpleasant symptoms associated with it. Therefore, how much oxygen is contained in the air, so much is needed for healthy full breathing.

3. Argon

Argon in the air takes the third place, it has no smell, color and taste. A significant biological role of this gas has not been identified, but it has a narcotic effect and is even considered doping. Argon extracted from the atmosphere is used in industry, medicine, for creating an artificial atmosphere, chemical synthesis, fire fighting, creating lasers, etc.

4. Carbon dioxide

Carbon dioxide makes up the atmosphere of Venus and Mars, its percentage in the earth's air is much lower. At the same time, a huge amount of carbon dioxide is contained in the ocean, it is regularly supplied by all breathing organisms, and is emitted due to the work of industry. In human life, carbon dioxide is used in fire fighting, the food industry as a gas and as a food additive E290 - a preservative and baking powder. In solid form, carbon dioxide is one of the most well-known dry ice refrigerants.

5. Neon

The same mysterious light of disco lanterns, bright signs and modern headlights use the fifth most common chemical element, which is also inhaled by a person - neon. Like many inert gases, neon has a narcotic effect on a person at a certain pressure, but it is this gas that is used in the preparation of divers and other people working at elevated pressure. Also, neon-helium mixtures are used in medicine for respiratory disorders, neon itself is used for cooling, in the production of signal lights and those same neon lamps. However, contrary to the stereotype, neon light is not blue, but red. All other colors give lamps with other gases.

6. Methane

Methane and air have a very ancient history: in the primary atmosphere, even before the appearance of man, methane was in much greater quantities. Now this gas, extracted and used as a fuel and raw material in production, is not so widely distributed in the atmosphere, but is still emitted from the Earth. Modern research establishes the role of methane in the respiration and life of the human body, but there are no authoritative data on this subject yet.

7. Helium

Looking at how much helium is in the air, anyone will understand that this gas is not one of the most important in importance. Indeed, it is difficult to determine the biological significance of this gas. Not counting the funny distortion of the voice when inhaling helium from a balloon 🙂 However, helium is widely used in industry: in metallurgy, the food industry, for filling balloons and meteorological probes, in lasers, nuclear reactors, etc.

8. Krypton

We are not talking about the birthplace of Superman 🙂 Krypton is an inert gas that is three times heavier than air, chemically inert, extracted from air, used in incandescent lamps, lasers and is still being actively studied. Of the interesting properties of krypton, it is worth noting that at a pressure of 3.5 atmospheres it has a narcotic effect on a person, and at 6 atmospheres it acquires a pungent odor.

9. Hydrogen

Hydrogen in the air occupies 0.00005% by volume and 0.00008% by mass, but at the same time it is the most abundant element in the universe. It is quite possible to write a separate article about its history, production and application, so now we will limit ourselves to a small list of industries: chemical, fuel, food industries, aviation, meteorology, electric power industry.

10. Xenon

The latter is in the composition of air, which was originally considered to be only an admixture to krypton. Its name translates as "alien", and the percentage of content both on Earth and beyond is minimal, which led to its high cost. Now xenon is essential: the production of powerful and pulsed light sources, diagnostics and anesthesia in medicine, spacecraft engines, rocket fuel. In addition, when inhaled, xenon significantly lowers the voice (the opposite effect of helium), and more recently, inhalation of this gas has been added to the doping list.

The air that makes up the earth's atmosphere is a mixture of gases. Dry atmospheric air contains: oxygen 20.95%, nitrogen 78.09%, carbon dioxide 0.03%. In addition, atmospheric air contains argon, helium, neon, krypton, hydrogen, xenon and other gases. Ozone, nitric oxide, iodine, methane, and water vapor are present in small amounts in the atmospheric air.

In addition to the constant components of the atmosphere, it contains a variety of pollution introduced into the atmosphere by human production activities.

1. An important component of atmospheric air is oxygen , the amount of which in the earth's atmosphere is 1.18 × 10 15 tons. A constant oxygen content is maintained due to continuous processes of its exchange in nature. On the one hand, oxygen is consumed during the respiration of humans and animals, is spent on maintaining the processes of combustion and oxidation, on the other hand, it enters the atmosphere due to the processes of plant photosynthesis. Land plants and phytoplankton of the oceans fully restore the natural loss of oxygen. With a drop in the partial pressure of oxygen, the phenomena of oxygen starvation can develop, which is observed when ascending to a height. The critical level is the partial pressure of oxygen below 110 mmHg. Art. Reducing the partial pressure of oxygen to 50-60 mm Hg. Art. usually incompatible with life. Under the influence of short-wave UV radiation with a wavelength of less than 200 nm, oxygen molecules dissociate to form atomic oxygen. The newly formed oxygen atoms are added to the neutral formula of oxygen, forming ozone . Simultaneously with the formation of ozone, its decay occurs. The general biological significance of ozone is great: it absorbs short-wave UV radiation, which has a detrimental effect on biological objects. At the same time, ozone absorbs infrared radiation coming from the Earth, and thus prevents excessive cooling of its surface. Ozone concentrations are unevenly distributed along the height. Its greatest amount is noted at the level of 20-30 km from the Earth's surface.

2. Nitrogen in terms of quantitative content, it is the most significant component of atmospheric air; it belongs to inert gases. Life is impossible in a nitrogen atmosphere. Air nitrogen is assimilated by certain types of soil bacteria (nitrogen-fixing bacteria), as well as by blue-green algae; under the influence of electrical discharges, it turns into nitrogen oxides, which, falling out with atmospheric precipitation, enrich the soil with salts of nitrous and nitric acids. Under the influence of soil bacteria, nitrous acid salts are converted into nitric acid salts, which in turn are absorbed by plants and serve for protein synthesis. Along with the assimilation of nitrogen in nature, it is released into the atmosphere. Free nitrogen is formed during the combustion of wood, coal, oil; a small amount of it is formed during the decomposition of organic compounds. Thus, in nature there is a continuous circulation, as a result of which the nitrogen of the atmosphere is converted into organic compounds, restored and enters the atmosphere, then is again bound by biological objects.

Nitrogen is necessary as an oxygen diluent, since breathing pure oxygen leads to irreversible changes in the body.

However, an increased content of nitrogen in the inhaled air contributes to the onset of hypoxia due to a decrease in the partial pressure of oxygen. With an increase in the nitrogen content in the air to 93%, death occurs.

In addition to nitrogen, the inert gases of air include argon, neon, helium, krypton and xenon. Chemically, these gases are inert, they dissolve in body fluids depending on the partial pressure, the absolute amount of these gases in the blood and tissues of the body is negligible.

3. An important component of atmospheric air is carbon dioxide (carbon dioxide, carbonic acid). In nature, carbon dioxide is in free and bound states in the amount of 146 billion tons, of which only 1.8% of its total amount is contained in atmospheric air. Most of it (up to 70%) is in a dissolved state in the water of the seas and oceans. Some mineral compounds, limestones and dolomites contain about 22% of the total amount of dioxide and carbon. The rest of the amount falls on the animal and plant world, coal, oil and humus.

Under natural conditions, there are continuous processes of release and absorption of carbon dioxide. It is released into the atmosphere due to the respiration of humans and animals, the processes of combustion, decay and fermentation, during the industrial roasting of limestones and dolomites, etc. At the same time, processes of assimilation of carbon dioxide are going on in nature, which is absorbed by plants in the process of photosynthesis.

Carbon dioxide plays an important role in the life of animals and humans, being a physiological causative agent of the respiratory center.

When high concentrations of carbon dioxide are inhaled, the redox processes in the body are disturbed. With an increase in its content in the inhaled air up to 4%, headaches, tinnitus, palpitations, and an excited state are noted; at 8% death occurs.

From a hygienic point of view, the content of carbon dioxide is an important indicator by which the degree of air purity in residential and public buildings is judged. The accumulation of large amounts of it in indoor air indicates sanitary problems (crowding, poor ventilation).

Under normal conditions, with natural ventilation of the premises and infiltration of outdoor air through the pores of building materials, the content of carbon dioxide in the air of residential premises does not exceed 0.2%. With an increase in its concentration in the room, a deterioration in the well-being of a person, a decrease in working capacity, may be noted. This is explained by the fact that simultaneously with an increase in the amount of carbon dioxide in the air of residential and public buildings, other properties of the air worsen: its temperature and humidity increase, gaseous products of human vital activity appear, the so-called anthropotoxins (mercaptan, indole, hydrogen sulfide, ammonia).

With an increase in the content of CO 2 in the air and the deterioration of meteorological conditions in residential and public buildings, the ionization regime of the air changes (an increase in the number of heavy and a decrease in the number of light ions), which is explained by the absorption of light ions during breathing and contact with the skin, as well as the intake of heavy ions with exhaled air.

The maximum allowable concentration of carbon dioxide in the air of medical institutions should be considered 0.07%, in the air of residential and public buildings - 0.1%. The latter value is taken as a calculated one when determining the efficiency of ventilation in residential and public buildings.

4. In addition to the main components, atmospheric air contains gases released as a result of natural processes occurring on the surface of the Earth and in the atmosphere.

Hydrogen contained in the air in an amount of 0.00005%. It is formed in the high layers of the atmosphere due to the photochemical decomposition of water molecules into oxygen and hydrogen. Hydrogen does not support respiration, in a free state it is not absorbed and is not released by biological objects. In addition to hydrogen, atmospheric air contains a small amount of methane; usually the concentration of methane in the air does not exceed 0.00022%. Methane is released during anaerobic decay of organic compounds. As an integral part, it is part of natural gas and gas from oil wells. When inhaling air containing methane in high concentrations, death from asphyxia is possible.

As a decomposition product of organic substances, small amounts of ammonia. Its concentrations depend on the degree of contamination of the area with sewage and organic emissions. In winter, due to the slowdown in the processes of decay, the concentration of ammonia is somewhat lower than in summer. During anaerobic processes of decomposition of sulfur-containing organic substances, the formation of hydrogen sulfide, which, in low concentrations, gives the air an unpleasant odor. In atmospheric air, iodine and hydrogen peroxide can be found in small concentrations. Iodine enters the atmospheric air due to the presence of the smallest droplets of sea water and seaweed. Due to the interaction of UV rays with air molecules, hydrogen peroxide; together with ozone, it contributes to the oxidation of organic substances in the atmosphere.

In the atmospheric air are suspended matter, which are represented by dust of natural and artificial origin. The composition of natural dust includes cosmic, volcanic, ground, sea dust and dust generated during forest fires.

Natural processes play an important role in the release of the atmosphere from suspended solids. self-cleaning, among which the dilution of pollution by convection air currents near the Earth's surface is of significant importance. An essential element of self-purification of the atmosphere is the precipitation of large particles of dust and soot from the air (sedimentation). As the altitude increases, the amount of dust decreases; at a height of 7 - 8 km from the Earth's surface, there is no dust of terrestrial origin. Significant Precipitation plays a role in self-cleaning processes, increasing the amount of settled soot and dust. The dust content in the atmospheric air is affected by meteorological conditions and aerosol dispersion. Coarse dust with a particle diameter of more than 10 microns falls out quickly, fine dust with a particle diameter of less than 0.1 microns practically does not fall out and is in suspension.