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 integral part of air. With its direct participation, all oxidative processes in the human and animal body proceed. At rest, a person consumes about 350 ml of oxygen per minute, and during heavy physical work, the amount of oxygen consumed increases several times.

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

In the atmosphere, the oxygen content does not change significantly. Plants absorb carbon dioxide and break it down to absorb carbon, and the released oxygen is released into the atmosphere. The source of oxygen formation is also the photochemical decomposition of water vapor in the upper atmosphere under the influence of ultraviolet radiation from the sun. In ensuring a constant composition of atmospheric air, the mixing of air flows in the lower layers of the atmosphere is also important. The exception is hermetically sealed rooms, where, due to the long stay of people, the oxygen content can significantly decrease (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 the alveolar air to the blood and from the blood to the tissue fluid occurs under the influence of a difference in partial pressure. The partial pressure of oxygen decreases with increasing elevation above sea level (Table 1).

Table 1. Partial pressure of oxygen at different altitudes

Of great importance is the use of oxygen for the treatment of diseases accompanied by oxygen starvation (oxygen tents, inhalers).

Carbon dioxide. The content of carbon dioxide in the atmosphere is fairly constant. This constancy is explained by its circulation in nature. Despite the fact that the processes of decay and the vital activity of the organism 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. At the same time, carbon goes to the construction of organic substances, and oxygen enters the atmosphere. Exhaled air contains up to 4.4% carbon dioxide.

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

Carbon dioxide also has hygienic significance. According to its content, the purity of the air in residential and public premises (i.e., premises where people are located) is judged. When people accumulate in poorly ventilated rooms, in parallel with 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 content of carbon dioxide 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 changes in the listed properties of air in residential premises and an increase in the concentration of carbon dioxide, as well as the simplicity of determining its content, make it possible to use this indicator for hygienic assessment of air quality and the efficiency of ventilation in public premises.

nitrogen and other gases. Nitrogen is the main component of atmospheric air. In the body, it is in a dissolved state in the blood and tissue fluids, but does not take part in chemical reactions.

At present, it has been experimentally established that, under conditions of high pressure, air nitrogen causes in animals a disorder of neuromuscular coordination, subsequent excitation and a narcotic state. Researchers observed similar phenomena in divers. The use of a helium-oxygen mixture for divers' breathing 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 of the sun, a small amount of other gases is formed in the air. Their hygienic value is relatively small.

* 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.

We all know very well that not a single living being can live on earth without air. 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 the life of the 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 the energy that is needed for life is released. 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 large cities, the percentage of carbon dioxide 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 a chemical element of the periodic table of 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 the sea and fresh waters of the whole 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. The physical properties of carbon dioxide are that it does not exist in a liquid state at normal atmospheric pressure, but immediately passes from a solid state to a gaseous state.

Carbon dioxide in the solid state is also called dry ice. To date, carbon dioxide is a participant in 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 one in 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 conduct a chemical analysis of air or other laboratory research, including, you can in our laboratory "EcoTestExpress".

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 inhales air with an increased level of oxygen for a long time, this 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 the modern world, a huge number of industrial facilities that pollute our air have recently been increasingly calling for the need to protect the environment, as well as monitor the purity of the air. 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 there are external factors to blame, 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.

Atmospheric air is a mixture of various gases - oxygen, nitrogen, carbon dioxide, water vapor, ozone, inert gases, etc. The most important part of the air is oxygen. The inhaled air contains 20.7% oxygen. It is necessary for the implementation of oxidative processes in the body. A person consumes about 12 liters of oxygen per hour, the need for it increases during physical work. The oxygen content in enclosed spaces below 17% is an unfavorable indicator, at 13-14% oxygen starvation occurs, at 7-8% - death. In the exhaled air, the amount of oxygen is 15-16%.

Carbon dioxide (CO2) is usually 0.03-0.04% of the air. Exhaled air contains 100 times more carbon, i.e. 3-4%. The maximum permissible content of carbon dioxide in indoor air is 0.1%. With insufficient ventilation of rooms where there are many people, the carbon dioxide content reaches 0.8%. At 1-1.5% CO2, there is a deterioration in health, a higher level of CO2 in the air can lead to significant health problems. Reducing the concentration of CO2 in the air is not dangerous.

Nitrogen (N2) is contained in the air at the level of 78.97 - 79.2%. It does not take part in the metabolic processes of living organisms and serves as a diluent for other gases, mainly oxygen. Air nitrogen takes part in the nitrogen cycle in nature.

Ozone (O3) is usually contained in the near-Earth air in very small doses (0.01-0.06 mg/m3). It is formed during electrical discharges during a thunderstorm. The cleaner the air, the more ozone, this is observed in the mountains, in coniferous forests. Ozone has a beneficial effect on the human body. Ozone is used for water disinfection and air deodorization, as it has a strong oxidizing effect due to the release of atomic oxygen.

Inert gases - argon, krypton and others have no physiological significance.
harmful impurities. Gaseous impurities and suspended particles enter the air as a result of human activities. The most common gaseous air pollutants are carbon monoxide, sulfur dioxide, ammonia and nitrogen oxides, hydrogen sulfide. At catering establishments, air pollution is possible by products of incomplete combustion of fuel, gas mixture (in gasified kitchens), gases (NH3, H2S) released during decay, ammonia (when using ammonia refrigeration units). During the heat treatment of food, the release of a highly toxic substance acrolein, as well as volatile fatty acids, is possible.

Carbon monoxide (CO) is formed during incomplete combustion of fuel, is part of combustible gas mixtures, has no smell and causes both acute and chronic poisoning. In gasified kitchens, it accumulates when gas leaks from the network or when it is not completely burned. The maximum concentration of CO in the atmospheric air, which can be allowed, is 1 mg/m3 (average per day), while the content of 20–100 mg/m3CO is allowed for the working area, depending on the duration of work.

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. 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 it 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 destruction of forests inevitably reduces the ingress of oxygen into the atmosphere, thereby disturbing its balance.

Ordinary atmospheric air, suitable for the breathing of people and other living beings, is a multicomponent mixture of gases. The main part of its volume is nitrogen, the share of which reaches approximately 78%. In second place in this indicator is oxygen, which accounts for about 21% of the volume of air. Thus, in total, these two gases make up about 99% of the volume of air.

The remaining 1-1.5% of the volume is mostly argon and carbon dioxide, as well as a small amount of other gases - neon, helium, xenon and others. At the same time, the proportion of carbon dioxide in ordinary atmospheric air, which is not subject to any influence, most often is about 0.3% by volume.

Exhaled air

At the same time, the composition of the air, which is obtained as a result of the human respiratory process, differs significantly from the original one in terms of the content of a number of elements. So, it is known that in the process of breathing the human body consumes oxygen, therefore it is natural that its amount in exhaled air is significantly less than in inhaled air. If the initial composition of the air contained about 21% oxygen, then in the air on exhalation it will be only about 15.4%.

Another significant change that occurs to the air during breathing concerns the content of carbon dioxide. So, if in the air entering the human body, its content usually does not exceed 0.3% of the volume, then in the air leaving the body the volume of carbon dioxide reaches 4%. This is due to the fact that during the functioning of the human body, its organs and tissues emit carbon dioxide, which is excreted during respiration. But the content of other gases in the exhaled air practically does not change in relation to the original. This is due to the fact that for the human body they are inert, that is, they do not interact with it in any way - they are not absorbed and not excreted.

It should be borne in mind that the air exhaled by a person changes not only its composition, but also some physical characteristics. Its temperature approaches the temperature of the human body, which is normally 36.6 ° C. Thus, if a person inhaled cold air, his temperature will rise, and if hot, it will decrease. In addition, exhaled air is usually characterized by a higher level of humidity compared to inhaled air.