The rationing of the air exchange rate and the concentration of co2. Labor protection: rules and norms of the environment for office premises

15.08.2016

The influence of carbon dioxide (CO 2) on the human body has long been known and well studied by many domestic and foreign experts. This relatively harmless gas according to GOST 12.1.007-76 belongs to the 4th class of danger, it is contained in small amounts in the composition of pure atmospheric air. Carbon dioxide, as already mentioned, is harmless in itself, but in concentrations of 7% it can damage a person's health in the form of suffocation. It should be noted that it does not have a cumulative effect, and all symptoms quickly pass with a decrease in its concentration.

Concentration of CO 2 in the range from 0.1% has a negative effect on the person's well-being. It is believed that the content of carbon dioxide from 0.04 to 0.07% is fresh air; from 0,07 to 0,1% - stale air, but this concentration is still permissible; more than 0,1% - sharply reduces the working capacity of the body. It should be noted that the change in the concentration of oxygen in the air can vary over a wide range from 19 to 21%, without affecting the health of a healthy person. ASHRAE has established an acceptable value of the carbon dioxide content in rooms with people staying: at a level of up to 1,000 ppm or 0.1% of the volume. Many international and domestic authors rely on this value when calculating air exchange.

In the European Standard of 2004, air in rooms with people staying is divided into quality categories from IDA 4 - low, IDA 2 and 3 - average, to IDA 1 - high. There are several ways to determine the quality category. Table 1 gives an example of one of the estimates for exceeding the level of CO 2, as an indicator, in indoor air above the outside air (Table 1).

Table 1.

	Exceeding the level of CO 2   in a room above its content in outdoor air, ppm
Room category	Typical range	Specify a value
IDA 1	<400	350
IDA 2	400–600	500
IDA 3	600–1 000	800
IDA 4	≥1000	1 200

Mechanical ventilation systems, where the CO 2 content was the dictating condition in the room served, are well developed and described by various experts. Systems natural ventilation in the old fund are designed for unorganized airflow through leakage of enclosing structures and infiltration of window openings. It should be noted that the general replacement of old windows with double-glazed windows led to a sharp change in the balance of supply air. In modern buildings, a supply valve is provided in the wall, but its construction is not always successful, and the inhabitants sometimes remove it.

Information on the actual indicators of the CO 2 content in the air of office premises or a residential fund is almost not available. To this end, a number of experiments were carried out, initially not claiming full coverage of the problem. The measurements are of an introductory nature for HVIS specialists, but at the same time reflect the main points of the problem.

The experiments were conducted in a residential building of Khrushchev's five-story building. The fencing structures are made of bricks. Two-room apartments of adjacent design with a total area of ​​43 m 2; number of inhabitants from 1 to 3. The apartments are equipped with natural ventilation systems and flues of gas water heating columns.

The apartments of the second and third floors were considered as the most characteristic. All apartments in which measurements were taken - with the replaced windows and double-glazed windows equipped with flaps of windows for ventilation. In the rooms with balconies there was a folding door.

The measurements were carried out in the center of the room at the level of the berth and the level of the head resting sitting areas. The device was at an altitude of 600 to 1000 mm.

All plants, to exclude their influence, were removed from the premises. Also, to exclude the effect of concentration exhaust from a human, the recorders were 1 meter from the person.

The experiment was carried out in the summer, on days:

for completely closed windows;

open in the room where the person is;

open in an adjacent room.

For the experiment, a CO 2 device was used. Carbon Dioxide Hygrometer Thermometer Data Logger Humidity Air Temp. Meter. With the help of this device, measurements of the level of CO 2 in a residential area, as well as the recording of data for measurement periods, were carried out.

Figure 1 shows the change in CO 2 concentration in a two-room apartment with fully closed windows and one person from 20:00 to 09:00 in the morning.

In Figure 1, the concentration is presented in ppm, registration with a 5-minute interval.

From the beginning of the measurements, there are fluctuations, followed by a gradual increase in CO 2 concentration in the residential area. The maximum content of carbon dioxide (1210 ppm) is fixed at about 5 am, after which some stabilization occurs. It is worth noting that the conditions throughout the measurement did not change. From which it follows that under unchanged conditions in an unventilated room, the concentration of CO 2 increases to a certain level and stabilizes.

With constant forced ventilation by a household fan with a capacity of 170 m 3 / h, the concentration of CO 2 in the room air varies from 400 to 550 ppm during the day. Let's consider in more detail the mode of ventilation.

Figure 2 shows the ventilation mode with a recording period of 5 minutes.

Fig.2 Change in the concentration of CO 2 in the apartment in the mode of ventilation with a recording period of 5 minutes, where the Oy axis is the concentration level of CO 2 in ppm, and the Ox axis is the time of the experiment.

With the open flap of the window in the first five minutes of airing, there is a rapid decrease in the level of CO 2 from 1210 to 900 ppm. Then the decline is more smooth and reaches its minimum value (500 ppm) 55 minutes after the beginning of the ventilation.

For more detail, a recording was made with a minute recording in the accumulation and ventilation mode (Figure 3).

Fig.3 Change in the concentration of CO 2 in the apartment with a minute recording, where the Oy axis is the concentration level of CO 2 in ppm, and the Ox axis is the time of the experiment.

At 23:20 all the windows were closed, at 03:30 the flap of the window was opened for ventilation, at 6:00 - it was left on micro airing. From 3:45, the decrease in CO 2 concentration began with some delay (it reached the recommended 500 ppm values ​​at 04:53). At the same time, the decline to 700 ppm was less than 10 minutes. In the morning and afternoon hours, the level of CO 2 in the room was practically unchanged. The evening peak (from 15:00 to 16:00) of the CO 2 concentration is due to the inclusion of the gas column and cooking, at 16:02 the window was completely opened for ventilation. The temperature in the room fluctuated from 22.5 to 26.3 ° C. Humidity ranged from 41.7 to 63.9%.

The measurements were carried out by microvoiring the room throughout the experiment. According to the graph presented in Figure 4, it can be seen that an increase in the level of CO 2 is observed during the night hours (from 0:40 to 3:40). After reaching the maximum value of the indicator - 820 ppm, the decline in the concentration of carbon dioxide in the room begins. Having reached the level of 480 ppm, the indicator stabilizes. It should be noted that the maximum values ​​of the concentration of CO 2 during micro-ventilation at night are still lower than in a similar measurement of the CO 2 level in the absence of ventilation (the difference in values ​​is approximately 400 ppm).

Fig.5 Change in the concentration of CO 2 in the apartment during micro-ventilation of the room, where the Oy axis is the concentration level of CO 2 in ppm, and the Ox axis is the time of the experiment.

Figure 5 shows the CO 2 content in a room with micro-ventilation and one person in this room. The experiment was carried out from 1:51 to 12:46. The concentration of carbon dioxide throughout the entire measurement period is practically unchanged. Humidity during the experiment in the room was 54-57%, the difference between internal and external temperature - no more than 5 ° C. In the room, the temperature ranged from 23.6 to 24.5 ° C.

   Based on the results of the experiments, the following conclusions can be drawn:

The concentration of carbon dioxide in a residential building at the dimensions of the construction and the conditions created for the experiment increases not to infinity, but the maximum level of CO 2 reaches in unventilated rooms.

The growth of CO 2 in time is not linear in exponential, the fall of CO 2 is also not linear.

Full ventilation without forced ventilation occurs in more than an hour, ventilating to an acceptable level - for 10 minutes. At the same time, an increase in the concentration of CO 2 in a residential building after full ventilation occurs in three or more hours.

Airing the living room in three hours is able to maintain the level of CO 2 in the air at an acceptable level.

Bibliography:

GOST 8050-85. Carbon dioxide is gaseous and liquid. Technical specifications.

Standard EN 13779: 2004. Ventilation for non-residential buildings - Performance requirements for ventilation and room-conditioning systems.

D. S. Robertson. The rise in the atmospheric concentration of carbondioxide and the effects of human health. Med. Hypotheses, 2001, 56.

The article was prepared by:
Popov Mikhail Ivanovich - Candidate of Technical Sciences. Head of the department "Production and operation of heat and gas supply and ventilation systems" in SPbGASU.

27.05.2011

Source: "S-O-K" magazine. Gurin I.V.

The modern person is almost 90% of the time in the room. The mothers are sent to the kindergarten, where groups are often crowded, students and students sit in classrooms for 40 people or more, and adults spend much longer than eight hours a day in the workplace. When you enter a room where there are a lot of people, you almost always feel that it's harder to breathe there than outside. I want to say "not enough oxygen", It's not true - oxygen is still more than enough, but in the room the concentration of carbon dioxide has increased. What happens in this case with our body? How harmful is it? Modern research proves that the increased content of CO2 in the inspired air adversely affects blood, mucous membranes, respiratory and urinary systems, bone tissue, immunity and mental activity of a person.

Figures

It is best to breathe in nature. In clean country air, 380-400 ppm of carbon dioxide, i.e. 0.038-0.04%. These concentrations are optimal for human respiration. The content of carbon dioxide in the air for the past 50 years has increased by 20% and is constantly growing - especially in large cities due to car exhausts and industrial emissions. Today, the level of CO2 in the air of a large city can be 600 ppm (0.06%) and higher. We will not discuss the atmosphere in detail: it is important for us that this happens in the premises where we spend almost all the time. Closed rooms are a kind of CO2 trap. Air with already elevated or even normal content of carbon dioxide comes through windows and ventilation, and then its concentration begins to grow rapidly due to the breathing of people who are in the building. There are aggravating circumstances here: forced ventilation may not be at all or it works poorly, and the natural one does not work, because the plastic windows do not let in air and they are closed so that no one gets a cold.

Indoors, the level of carbon dioxide rises much faster than oxygen decreases. Measurements show that even when in the classroom the CO2 level reaches 1000 ppm (0.1%), the oxygen content remains practically unchanged. Of course, the increase in carbon dioxide depends on the number of people in this room, on their weight and what they do. The gym will become stifling much faster than in the office (Table 1).

Researchers know that there is a connection between the concentration of CO2 and the feeling of stuffiness. The person begins to feel the symptoms of "lack of fresh air" (and in fact an increased concentration of carbon dioxide) already at its level of 0.08%, i.е. 800 ppm. However, in modern offices there are also 2000 ppm of CO2 and higher. But more on that later.

Exhaled man's carbon dioxide

Table 1

What is acidosis and why is it bad?

Normally, the pH of the human blood is approximately 7.4. Our body is tuned to this figure, it is necessary for the work of all the enzyme and biological systems of the body. It is logical to assume that even small constant changes in the acidity of blood can have a very strong effect on a living being.

What happens when an increase in the concentration of CO2 in the air that enters the body? The partial pressure of CO2 in our alveoli increases, its solubility in the blood rises, and a weak carbonic acid (CO2 + H2O = H2CO3) is formed, which in turn decomposes into H + and HCOO3-. Blood is acidified, which is scientifically called acidosis. The higher the concentration of CO2 in the air, which we constantly breathe, the lower the pH of the blood and the more acid reaction it has (Figure 1).

Minimal physiological consequences of acidosis are overexcitation, heart palpitations and a moderate increase in pressure. With a stronger acidosis, a person becomes sluggish, drowsy, and feels anxious. But all this happens already at the concentrations of carbon dioxide, typical for modern premises, where there are a lot of people. However, when a person goes to fresh air for a long time, his condition gradually comes back to normal.

And if you breathe air all your life, in which there is a lot of carbon dioxide, daily, for 20 hours and more? When acidosis occurs biochemical changes in the body, if it is chronic, then, apparently, they at some point may become irreversible. In what exactly - scientists have yet to find out. For the constant concentration of hydrogen ions within the body, its buffer systems respond. In particular, a big role here is played by the kidneys, which deduce an excess of unnecessary substances. The body also has inorganic buffers. Some of the most important are bicarbonate (NSO-3) and phosphates. There are other, organic, such as hemoglobin and plasma proteins. But still 53% of the total buffer capacity of blood is in the "bicarbonate-CO2" system (the bicarbonate content in the plasma is 24 mmol / l).

When acidosis begins, the body first defends itself, increasing the concentration of bicarbonate in the blood plasma, as evidenced by numerous biochemical studies. To compensate for acidosis, the kidneys intensively secrete H + and delay HCCO3-. Strictly speaking, the concentration of CO2 at which the increase in bicarbonate in the blood begins, could become one of the scientifically valid norms for the allowable content of carbon dioxide in the premises. Then other buffer systems are turned on, and the secondary biochemical reactions of the organism are much more complicated (we will not go into details in detail, the mechanism is rather complicated). Because of weak acids, incl. and coal (H2SO3), can form weakly soluble compounds (CaCO3) with metal ions, they are deposited in the form of stones, primarily in the kidneys. Fortunately, a person spends in a stuffy place not all the time, so this process is reversible - after some time after entering the fresh air calcium carbonate should dissolve.

Karl Schafer, an employee of the Medical Research Laboratory of the US Navy Submarine Fleet, investigated how different concentrations of carbon dioxide affect guinea pigs. Rodents were kept for eight weeks at 0.5% CO2 (oxygen was normal - 21%), after which they had significant calcification of the kidneys. It was noted even after long exposure to guinea pigs of lower concentrations - 0.3% CO2 (3000 ppm). But that is not all. Shafer and his colleagues found in the guinea pigs after eight weeks of 1% CO 2 demineralization of the bones, as well as structural changes in the lungs. The researchers regarded these diseases as an adaptation of the organism to the chronic effects of CO2. If scientists gave the experimental animals enough time to recover (more than a month), then these signs disappeared. However, the researchers themselves say that further experiments are needed to establish how the lower concentrations of carbon dioxide will affect the mammal state and when the changes in their organisms become irreversible.

Other effects and sick building syndrome

Research scientists are not limited to acidosis. A survey of 344 employees in 86 offices in Taipei City (Taiwan) showed that already at a CO2 level of more than 800 ppm (0.08%), they had a rise in oxidative stress markers, for example, 8-OHdG (8-hydroxy-2-deoxy- guanosine), determined in urine. The content of markers is the higher, the longer a person is in a stuffy room. The same volatile organic compounds act on the human body, and they and carbon dioxide intensify each other's negative influence.

The EU scientists checked the health of students in a room with a carbon dioxide concentration\u003e 1000 ppm, or 0.1%. (There are almost two thirds of such classes in the West, and in quite prosperous countries - in Sweden, Norway, Denmark and France.) 547 schoolchildren aged 9 to 10 years were evaluated in biomedical tests for respiratory and allergic conditions. It turned out that children spending a lot of time in a room with a high level of CO2, 3.5 times more likely to have a dry cough and twice as many get sick with rhinitis.

Korean scientists also investigated the effect of CO2 on asthmatics. The sample consists of 181 children under the age of 14 from 110 houses and apartments in Seoul. The rooms measured the level of substances considered to be the main air pollutants: CO, NO, house dust mite allergens, cockroaches, mold spores and CO2 fungi. Scientists concluded that only elevated concentrations of CO2 increased asthma attacks in children. By the way, respiratory infections and asthma are considered the main diseases of schoolchildren.

If we recall the primary signs of acidosis, we will understand why sluggish and sleepy schoolchildren do not perceive well new material.

The problem of an increased level of CO2 is also characteristic of kindergartens, especially for bedrooms. Fortunately, the schoolchildren every 45 minutes there is a change during which they are expelled from the classroom, and a quiet hour with closed room windows is not very long.

Where can I get to be an adult? In many institutions work very poorly forced ventilation  - it is here that the cause of COO is overclocked. We have already said that plastic windows isolate heat and sound well, but completely deprive the room of natural ventilation, turning it into a large cellophane bag. The level of carbon dioxide in this "package" is growing very rapidly.

There are buildings that are called sick in special literature, and people working there experience sick building syndrome (SBS). The syndrome has many manifestations: irritation of the mucous membranes, dry cough, headache, decreased efficiency, inflammation of the eyes, nasal congestion, difficulty concentrating. This problem is familiar to residents of the EEC, the United States, Canada and many other countries. Some researchers believe that it is carbon dioxide that is one of the main causes of the development of SBS and this syndrome appears already at its level in excess of 800-1000 ppm. Why did they decide that the culprit was carbon dioxide? Because when in the office room its concentration dropped below 800 ppm (0.08%), then the symptoms of SBS became weaker. In addition, the level of impurities that could cause such symptoms increases significantly more slowly than the CO2 level, as people constantly exhale it.

About the syndrome of the sick building began to speak after there were houses with good thermal insulation and tightly closed windows, as well as a low level of ventilation due to energy savings. Of course, the causes of SBS may be the allocation of construction and finishing materials, substances that emit the human body, mold spores, etc. If the ventilation in the room is poor, then, of course, the concentration of these substances in the room will also increase, but more slowly than CO2. Carbon dioxide acts as a thin indicator - it indicates that the level of ventilation is insufficient, which means that the concentration of other pollutants will also grow.

Specialists at Middlesex University (UK), after a thorough investigation involving 300 people, issued a verdict: the carbon dioxide level in the office should not exceed 600-800 ppm (0.06-0.08%). If it is higher, then attention is reduced by 30%. At CO2 concentrations of more than 1500 ppm 79% of the respondents experienced a feeling of fatigue, and more than 2000 ppm - two-thirds of the subjects could not concentrate. In 97% of employees suffering from migraine, it appeared already at a carbon dioxide level of 1000 ppm (0.1%).

Scientist from the UK DS. Robertson believes that people begin to feel the deterioration of air quality even at a CO2 concentration of 600 ppm, and not at 800, as mentioned at the beginning of the article. When it gets higher, individual people have one or more classic symptoms of carbon dioxide poisoning - breathing problems, rapid pulse, headache, hearing loss, sweating, fatigue, physiological disorders, and all of them grow in direct proportion to the CO2 level (Table 2 , Figure 2). According to other data, in 15-33% of people these symptoms occur at a concentration of CO2 600-800 ppm, in 33-50% - at 800-1000 ppm, and 100% will test them at a concentration of 1500 ppm. The design model says that in order to maintain CO2 600 in a CO2 room, 68 m 3 / h of air per person must be forced into it by forced ventilation.

How does the amount of carbon dioxide in the air affect a person

table 2

Level of CO2, ppm	Physiological manifestations
Atmospheric air 380-400	Perfect for health and well-being
400-600	Normal amount of air. Recommended for children's rooms, bedrooms, offices, schools and kindergartens
600-1000	There are complaints about air quality. People with asthma may get more seizures
Above 1000	General discomfort, weakness, headache, concentration of attention falls by a third, the number of errors in work increases. Can lead to negative changes in the blood, there may also be problems with the respiratory and circulatory system
Above 2000	The number of mistakes in work is greatly increased, 70% of employees can not concentrate on work.

How can we understand that this influence is CO2, and not other toxic products formed in the process of human life (including acetone, ammonia, amines, phenols)? In the University of Budapest, technology and economics have developed a special methodology that allows to minimize the level of pollution by other substances. It was confirmed that CO2 is to blame. The study involved young and healthy people, whose average age was 21 years, and, despite the fact that the experiments lasted no longer than 140-210 minutes (concentrations reached 3000 ppm), they felt frankly unimportant. What to say about employees who are in offices for eight to nine hours every day for many months and years.

In early 2009, Lawrence Berkeley National Laboratory staff (USA) tried to understand how carbon dioxide in concentrations of 550.1000 and 2500 ppm affects mental activity and human health. The experimental procedure was similar to that used by Hungarian scientists, but volunteers participating in this experiment were at the given CO 2 levels daily for eight hours for three months. The received data are still being processed, but the optimism is inspired by the fact that at last a clear standard of experiment has appeared.

Here is another important point: today the concentration level of CO2 in the room is the main indicator of air quality. It acts as an indicator gas, through which it is possible to judge not only about other pollutants, but also about how well the ventilation system in the building works.

Studies in the classroom showed that if there are, in addition to carbon dioxide, volatile organic compounds and formaldehydes in the air, then it is sufficient to follow only CO2. If ventilation copes with it, the remaining pollutants also remain at a low level. Moreover, according to CO2 it is possible to judge the amount of bacteria in the air. The more carbon dioxide, the worse the ventilation and the more air in the air of different bacteria and fungi. This is particularly noticeable in winter, when the intensity of ventilation decreases, and the number of respiratory infections increases.

Hidden problem

The problem of carbon dioxide in the room exists in all countries, but in Russia it seems to be like no. New buildings are being built, often with the use of modern "green" technologies, old buildings are modernized, new windows are put up. And people are uncomfortable, and the population of big cities is weaker and more sick. Doctors treat the consequences, sin on the general pollution of the atmosphere, and there are no strict norms for the maintenance of carbon dioxide in the premises in Russia.

For the last several decades, Russian studies on this subject have hardly appeared. Meanwhile, some measurements in Moscow offices showed that in some of them the CO2 level is 2000 ppm and higher. In the 1960s. the last century O.V. Eliseeva in her thesis carried out detailed studies to substantiate the MPC of CO2 in the air of residential and public buildings. She tested how carbon dioxide affects concentrations of 0.1% (1000 ppm) and 0.5% (5,000 ppm) on the human body, and concluded that short-term inhalation of carbon dioxide at healthy levels by healthy people causes clear shifts in the function external respiration, blood circulation and electrical activity of the brain. According to her recommendations, the content of CO2 in the air of residential and public buildings should not exceed 0.1% (1000 ppm), and the average content of CO2 should be about 0.05% (500 ppm). Despite the fact that even a short-term effect caused an undesirable effect, neither the MPC nor any other standards for carbon dioxide at that time were adopted in the USSR. There are no such norms for educational, office and residential premises in the SNiP and SanPiN.

In Europe, the USA and Canada, as a rule, the norm is 1000 ppm (0.1%). It is in accordance with these figures that the ventilation of buildings is calculated. Many schools monitor air quality by the level of carbon dioxide. Of course, this level does not always and not always correspond to the norm. But in this case, the school administration is obliged to take measures to improve the situation. In Finland, for example, a school in which classes an increased level of carbon dioxide is detected may even be closed until ventilation is established.

In general, in the West, the topic of indoor air quality is quite popular. Annually conferences are held on the topic "Healthy building" and the topic of ventilation there rises constantly. By the way, about ventilation systems. On the one hand, in the modern world, everyone is trying to save electricity, on the other - you need to maintain a good air exchange, and this requires a large number electric power. In Finland, scientists suggested removing carbon dioxide with the help of absorbers built into the ventilation systems. So, perhaps, it will be possible to achieve a reasonable balance between energy saving and a safe level of carbon dioxide in the premises. Such household absorbers of carbon dioxide for premises already exist, it would be the desire to apply them.

In recent years, projects of so-called "green" buildings have appeared in the USA and in Europe. They are built of environmentally friendly materials and should consume as little energy as possible or provide it themselves. Everything would be fine, but this inevitably leads to savings on ventilation. In December 2008, the British newspaper Daily Mail described how, as prof. Derek Clements-Krum investigated several schools that tried to implement the idea of ​​an eco-friendly building with minimal energy consumption. In these schools, the professor recorded a very high level of CO2 in the classrooms. As a result, the children were inhibited by the thought process, they were sluggish and could not normally learn.

There was information that the first "green" high-rise administrative and residential complex "Kristall" (187 thousand m 2) will also be built in the north-east of Moscow. If we consider that the problem of carbon dioxide in a room in Russia is unfamiliar, then people's health in this building can be feared.

In our school classes, forced ventilation is practically non-existent. Teachers should do "through ventilation" of the class during the change. True, it is cold in winter, and this is impossible. Even after airing, the level of carbon dioxide quickly grows several times, so by the middle of the lesson, children can not concentrate. In modern office buildings there is ventilation, but often in the construction of buildings count on a single number of workers, and then they are much more. By the way, if in the street CO2 becomes at some point very much, then we can not do without carbon dioxide absorbers.

In recent years, accurate infrared sensors have appeared to measure the level of carbon dioxide in the premises. They are part of gas analyzers and show the concentration of carbon dioxide in real time, so they are convenient to put in residential and public buildings, schools and kindergartens. However, in order to benefit from these measurements, clear standards for the level of carbon dioxide in the premises are needed. And we do not have them yet.

Norms of the maintenance of carbonic gas

Carbon dioxide is the norm in our country and in Europe.

In the magazine "ABOK", No. 4, 2008, an article by Yu. D. Gubernsky and Ye. O. Shilkroth "How much air does a person need for comfort?" Was published, which aroused great interest among specialists. The material presented in the article shows that although much attention is paid to the problem of rationing of air exchange over CO2, there is not enough material to solve this problem. This article suggests further discussion of this problem.

A few years ago in the domestic normative documents  when designing ventilation in rooms with people staying, CO2 was taken into account only indirectly in the specific norms of air exchange. In foreign standards, its concentration in indoor air serves as an indicator of the content of other more harmful contaminants and the corresponding intensity of ventilation. High concentrations of carbon dioxide and other gases in the outdoor air of large cities lead to the choice of either intensifying the air exchange, causing a chain reaction to increase energy consumption by burning organic fuels with additional air pollution (including CO2) or purifying the supply air from the gases. This corresponds to the latest research of scientists on the dangers of carbon dioxide for human health with an increase in concentration of two to three times compared to pure atmospheric air.

According to modern medicine, several hundred chemical compounds were found in the metabolic (vital activity) secretions of the human body, of which more than two hundred substances - from the skin surface and over a hundred - with exhaled air. One of the most interesting substances is carbon dioxide. This relatively harmless gas according to GOST 12.1.007-76 belongs to the 4th class of danger, it is contained in small amounts in the composition of pure atmospheric air. According to the data of most sources, its concentration is about 0.03% of the volume (v), that is, 1 m3 contains 0.3 L, or 0.3 / 22.4 = 0.01339 moles (according to the TSB - 0 , 0314% by volume). Knowing the molecular mass of nitrogen dioxide 44 g / mol, it is easy to determine its mass in 1 m3, namely: 44 x 0.01339 = 0.589 g. Concentration, respectively, is 589 mg / m3. In such quantities, carbon dioxide is essential for human life. According to GOST 8050-85 "Carbon dioxide is gaseous and liquid. Specification "the density of gaseous carbon dioxide is 1.839 kg / m3, that is, about 1.5 times more air. Table 1 lists formulas for transferring quantities from one unit to another. As in domestic regulatory documents, and in foreign countries there is no normative of the maximum permissible concentration of carbon dioxide in the atmospheric air. Obviously, the content of CO2 in the air will be different in rural areas, small and large cities. Background concentrations are determined by vehicle emissions, fuel combustion at thermal power plants and work industrial enterprises. The difficulty lies in the fact that there is no monitoring of the level of CO2 by the services of the Center for Hydrometeorology. Abroad, carbon dioxide, along with nitrogen oxides, carbon monoxide, sulfur dioxide and volatile organic compounds, is a typical pollutant that must be taken into account when evaluating outdoor air for the design of ventilation and air conditioning systems. The European standard EN 13779 "Ventilation for non-residential buildings - Performance requirements for ventilation and room-conditioning systems" as a general basic guideline proposes to take a concentration of carbon dioxide in the countryside of 350 ppm, in small towns 400 ppm, in urban centers 450 ppm. In fact, it can be much higher. For example, measurements in the center of Moscow in windless weather at the end of summer in the area of ​​the Garden Ring showed that with a fairly intensive traffic the CO2 level rose to 900 ppm (0.09% vol.). Having walked a few hours this concentration and without the instruments will feel on everyone in the form of a headache. Table 1

Units of measurement of gas concentrations and their
  reciprocal recount

Cx mg / m3% (v / v) ppm,
  cm3 / m3

(parts per million)

mg / m3 1 8312.6 10-4 CaT / M P 8312.6 CaT / M P

% (v / v) 0.12 101 Ca
  М Р / Т 1 104 Са

(parts per million) 0.12 10-3Ca MF / T 10-4
  Ca 1

Note:

Ca
  - numerical value of concentration in given units;

C
  - numerical value of concentration in the desired units;

M
  - molecular weight of gas;

R
  - total pressure of the gas mixture, Pa;

T
  - temperature, ° K.

One of the methods widely used in the West to determine the required intensity of air exchange in public buildings is the use of carbon dioxide as an indicator of air quality. By its concentration, it is judged on the content of other substances released by humans, which are formed in relative concentrations (the ratio of the actual concentration to the MPC) is less. When the CO2 level is lowered by dilution with fresh air, the level of concentration of other substances simultaneously decreases. Carbon dioxide is chosen because its concentration is easy to measure with sufficient accuracy and its mass release is significantly higher than other harmful substances.

It is well known that one person in a calm state, for example an office worker, consumes 20-30 liters of oxygen per hour, with 18-25 liters of carbon dioxide, and in gym and gym classes - up to 36 liters or more. If in the inhaled air contains 0.03% (vol.) CO2, then in the exhaled air - 3.6% (vol.), That is, it increases more than 100 times. Intensively, carbon dioxide is released from the gas stove while cooking. As the CO2 content in the air increases above a certain value, a person begins to feel uncomfortable, may become drowsy, headaches, nausea, a feeling of suffocation. His influence is so gradual and weak that it is difficult to detect immediately. This limit is different for different people - men and women, children. However, until recently in the domestic documents there was no standard for indoor air quality for carbon dioxide. Only hygienic standards in 2006 introduced the maximum single MPC equal to 13 790 ppm (27 000 mg / m3) and an average of 4 597 ppm (9 000 mg / m3) for the air in the work area production facilities. For comparison: in the USA these figures are 30,000 ppm (58,740 mg / m3) and 5,000 ppm (9,790 mg / m3), respectively. In mines at workplaces, a concentration of 0.5% (by volume) or 5 000 ppm is allowed. In accordance with GOST 8050-85 "At concentrations of more than 5% carbon dioxide has a harmful effect on human health ... This reduces the volume fraction of oxygen in the air, which can cause the phenomenon of oxygen deficiency and suffocation." Recall that the maximum single and medium-term concentration of maximum permissible concentrations of air in the working area is determined by GOST 12.1.005-88 and hygienic standards GN 2.2.5.1313-03, GN 2.2.5.1314-03.

For residential and public buildings, this standard is still missing. The conflict arises due to the fact that in accordance with SNiP 41-01-2003 "Heating, ventilation and air conditioning", SanPiN 2.1.2.1002-00 "Sanitary and epidemiological requirements for residential buildings and premises", etc. for these premises the quality standard is assumed to be equal for the air of populated areas (GN 2.1.6.1338-03, GN 2.1.6.1339-03), which, as noted above, is absent. However, unlike many other pollutants that are practically not released in the premises, the content of carbon dioxide intensively increases. It is interesting that even in the manual of RV Shchekin in 1976, the calculation of the required air exchange for dilution of CO2 by one person is given.

The European Standard of 2004 proposes to divide the air in rooms with people staying on the quality category from IDA 4 - low, IDA 2 and 3 - medium, to IDA 1 - high. There are several ways to determine the quality category. One of them estimates the excess of CO2 level, as an indicator, in indoor air above the outside air (Table 2). Table 2

Typical range

IDA 2 400-600 500

IDA 3 600-1
000 800

IDA 4? 1000 1 200

Knowing the location of the building ( countryside, city) and the level of CO2 concentration in outdoor air it is easy to determine its calculated content in the room air. The following are recommendations for the installation of certain classes of filters, usually at least two stages, to achieve the required air purity in accordance with the required IDA quality category. This applies not only to solid dust particles, but also to the main gases: NOx, SO2, polycyclic aromatic hydrocarbons and volatile organic compounds. The standard states: "In the urban environment, the use of molecular (gas) filters is recommended." It should be noted that according to the ASINKOM Association, the European standard was adopted without changes as domestic GOST R EN 13779-2007 "Ventilation in non-residential buildings. Technical requirements  to ventilation and air-conditioning ». FSUE STANDARTINFORM announced that it will come into force on October 1, 2008.

The acceptable acceptable value of carbon dioxide content in rooms with people staying was established by hygienists and was accepted, for example, by the ASHRAE 62-1989 standard at 1,000 ppm (1 958 mg / m3) or 0.1% (vol). This value is based on many authors in the calculation of air exchange. This value appears in SP 2.5.1198-03 "Sanitary rules for the organization of passenger transportation" for railway stations and SanPiN 2.5.1.051-96 "Working and recreational conditions for the flight crew of civil aviation" for aircraft cabs. Knowing the release of CO2 by one person in the office - 18 l / h (0.005 l / s) or 35 200 mg / h according to the formula (L.2) SNiP 41-01-2003, the required supply air flow for one person is equal to

L = 35 200 / (1 958 - 589) = 25.7 m3 / h.

In units of l / s and ppm, L = x 106 = 7.14 l / s.

The first domestic document, in which an attempt is made to regulate the content of CO2 in the outdoor and indoor air, is the ABOK standard "Residential and public buildings. Norms of air exchange. " The recommended reference is the maximum allowable concentration in outdoor air: the countryside is 332 ppm (650 mg / m3), small towns - 409 ppm (800 mg / m3), large cities - 511 ppm (1,000 mg / m3). The upper permissible limit of CO2 concentration in residential and public buildings should not exceed the concentration in the outside air by 638 ppm (1,250 mg / m3). In this case, the required air exchange per person is 28 m3 / h.

As a result of recent studies conducted by Indian scientists in the city of Calcutta, it was found that just like NO2, CO2 is potentially toxic to humans even at low concentrations, taking into account its effects on the cell membrane and biochemical changes such as increased stress CO2 in the blood, an increase in the concentration of bicarbonate ions in the blood and urine, acidosis, etc. To determine how the level of CO2 in the air affects human processes, measurements were made of the level of bicarbonate in the blood and in urine person. A total of 593 people were studied from the residential, commercial and industrial areas of the city and the control zone, located in ecologically clean countryside. The level of bicarbonate in the serum - the biological indicator of the effect of CO2 - was an average of 60% higher in Calcutta than in the rural areas, with the highest in the industrial zone. In the city of Calcutta, CO2 was present in air in concentrations from 0.03 to 0.06%. The level of ventilation in the premises was adequate in almost 75% of residential and working premises. Taking into account the fact that an increase in the level of CO2 in the atmosphere leads to an increase in its concentration in the air of the room, it can be said that it can cause an increase in the level of bicarbonate in the blood.

In his works, the English scientist D. S. Robertson writes that the level of carbon dioxide in the atmosphere at which mankind can survive is much lower than expected, so a level of carbon dioxide safe for humans needs revision. He calculated the maximum safe for human level of carbon dioxide in the atmosphere, which is 426 ppm. The scientist also believes that under the influence of carbon dioxide, the level of which is higher than the indicated figure, the pH value in the blood serum decreases, which leads to acidosis. Symptoms of the initial degree of acidosis are as follows: the state of overexcitation and moderate hypertension. Further, drowsiness and anxiety are added to them and, as a consequence, a decrease in the desire to exercise physical activity. There is a possibility that when the concentration of carbon dioxide in the atmosphere reaches 426 ppm, and this can happen earlier than in two generations, the health of at least some of the world's population will deteriorate.

Finnish scientists led by Olli Seppanen conducted 21 experiments on the basis of more than 30 000 subjects to study the effect of the concentration of carbon dioxide. If the level of carbon dioxide in the office space was below 800 ppm (0.08% vol.), Symptoms such as eye inflammation, nasal congestion, nasopharyngeal inflammation, problems associated with the respiratory system, headache, fatigue and difficulty with concentration, which occurred in employees at a higher concentration of CO2, significantly decreased.

In a press release of the annual conference of the European Respiratory Society in 2006, the results of studies conducted in five EEC countries by a group of Italian scientists were published. Studies have shown that 68% of children experience a negative impact of CO2 above 1,000 ppm. They experienced severe breathing, shortness of breath, dry cough and rhinitis more often than other children. The following conclusions were made: children who are in a room with a high CO2 level are 3.5 times more likely to have a dry cough and 2 times to develop rhinitis. They have a more vulnerable nasopharynx than their peers.

In a study by Korean scientists on the effect of CO2 concentration in a room on asthma attacks in children, in homes and apartments where children live with asthma, the levels of substances considered to be the main air pollutants in the room, such as CO, NO2, allergens and CO2, were measured. As a result of these studies, it was concluded that the most important factor affecting the onset of asthma attacks in children is only the level of CO2 concentration.

Taking the allowable concentration of CO2 in the outdoor air of a megacity of 450 ppm, and the optimal air exchange in an indoor air of 800 ppm, the required air exchange per person will be

L = 106 = 14.29
l / s = 51.4 m3 / h.

Actually, the concentration in the outside air can be even higher, and inside the room there can be other sources of CO2 emission, for example, when cooking. If the CO2 content in the outdoor and indoor air is 100 ppm, the required air exchange will be 180 m3 / person, which exceeds reasonable limits.

As one of the measures, the new American standard ANSI / ASHRAE Standard 62.1-2004 provides for a dynamic change in the operating modes of ventilation of residential and public buildings. This is realized by means of DCV (Demand-Controlled Ventilation, DCV), by regulating the amount of fresh air supplied in excess of the minimum required as the actual situation changes, determined by the number of people present inside the ventilated volume. An objective prerequisite for use in domestic practice is a significant reduction in the price of inverter fan speed control circuits over the past years through the use of increasingly affordable frequency-controlled drives. DCV technology is available in the article. However, this measure is not always possible to achieve an effective result.

On another measure to reduce the content of harmful gases in the air of the premises P. Ole Fanger wrote in his article: "Cleaning the internal air from gaseous pollutants is a promising method of improving air quality and partial replacement of ventilation. Various methods of air purification are being developed, including sorption and photocatalysis. It was shown that the latter method has a significant filtration efficiency, which was fixed during filtration of individual chemicals present in the air. For a typical mixture of hundreds of chemicals present inside the building in very small concentrations, using these two methods, the purification efficiency of more than 80% can be achievable, that is, cleaning can reduce the concentration of pollutants and improve indoor air quality fivefold. At the same time, it is obvious that additional cleaning technologies development and further research are needed to increase the efficiency of cleaning for typical sources of indoor air pollution. "

Photocatalytic oxidation (FFC) is a very promising technology for reducing volatile organic compounds (VOCs) in indoor air. However, studies conducted by the Berkeley National Laboratory in 2005 and 2007 showed that the photocatalytic oxidation method reduces the amount of VOC in the room air, but produces formaldehyde as a by-product. Scientists believe that for application of this method  further study is needed to either reduce the amount of formaldehyde and acetaldehyde produced by the reaction, or combine this technology with gas scrubbers to trap toxic by-products before they enter the room. To this, it must be added that the FKO does not remove carbon dioxide, but rather adds it to the room, since the final products of the reaction must be CO2 and water.

At present, the most safe for cleaning air from gases in the premises where people are located can be considered filters based on the method of adsorption of pollutants in the supply ventilation systems. As the filter element, activated carbon and highly efficient materials are used. Such filters are already offered in the climate market.

If the possibility of maintaining air quality at a high level with the help of ventilation systems is not possible, you can remove its excess by household adsorbers of carbon dioxide.

1.
  Carbon dioxide is toxic to humans even in relatively low concentrations. It can not be considered only as an indicator of the effectiveness of ventilation. The best for a person in a room is the level of carbon dioxide, as close as possible to the atmospheric.

2. Concentration of CO2 requires constant monitoring in the premises with people staying in industrial cities and large megacities where industry and transport constantly pollute the air with carbon dioxide and other gases. This is especially true for children's institutions and other public buildings.

3.
  The growth of carbon dioxide in the atmosphere, especially in large cities due to emissions of vehicles, energy and industry, necessitates an increase in air exchange in premises with people staying. This leads to increased energy costs and increased CO2 emissions when it is produced. The way out is to achieve a reasonable optimum between the amount of fresh air and the required purification of carbon dioxide and other gases.

In domestic regulatory documents when designing ventilation in rooms with people staying, CO2 was taken into account only indirectly in the specific norms of air exchange.

In foreign standards, its concentration in indoor air serves as an indicator of the content of other more harmful contaminants and the corresponding intensity of ventilation. High concentrations of carbon dioxide and other gases in the outside air of large cities lead to the choice of either intensifying air exchange, causing a chain reaction to increase energy consumption by burning organic fuels with additional atmospheric pollution (including CO 2) or purifying the supply air from the gases. This corresponds to the latest research of scientists on the dangers of carbon dioxide for human health with an increase in concentration of two to three times compared to pure atmospheric air.

Carbon dioxide is relatively harmless gas in accordance with GOST 12.1.007-76 belongs to the 4 th class of danger, it is contained in small amounts in the composition of pure atmospheric air. According to the data of the majority of sources, its concentration is about 0.03% of the volume (v), that is, 1 m 3 contains 0.3 l, or 0.3 / 22.4 = 0.01339 mole (according to the TSB - 0.0314% by volume). Knowing the molecular mass of nitrogen dioxide 44 g / mol, it is easy to determine its mass in 1 m 3, namely: 44 x 0.01339 = 0.589 g. Concentration, respectively, is 589 mg / m 3. In such quantities, carbon dioxide is essential for human life. According to GOST 8050-85 "Carbon dioxide is gaseous and liquid. Specifications "the density of carbon dioxide gas is 1.839 kg / m 3, that is, about 1.5 times more air. As in domestic regulatory documents, and in foreign countries there is no normative of the maximum permissible concentration of carbon dioxide in the atmospheric air. Obviously, the content of CO2 in the air will be different in rural areas, small and large cities. Background concentrations are determined by vehicle emissions, fuel combustion at thermal power plants and the operation of industrial enterprises. The difficulty lies in the fact that monitoring of the level of CO 2 by the services of the Center for Hydrometeorology is not conducted. Abroad, carbon dioxide, along with nitrogen oxides, carbon monoxide, sulfur dioxide and volatile organic compounds, is a typical pollutant that must be taken into account when evaluating outdoor air for the design of ventilation and air conditioning systems. European standard EN 13779 "Ventilation for -residential buildings - Performance requirementsforventilationandroom -conditioningsystems "as a common basic guide proposes to take the concentration of carbon dioxide in the countryside 350ppm, in small cities 400ppm, in city centers 450ppm. In fact, it can be much higher. For example, in the center of St. Petersburg, with a fairly intensive traffic, the level of CO 2 could rise to 900ppm (0.09% by volume). Walking for several hours, this concentration and without the instruments will be felt by everyone in the form of a headache.

The first domestic document, in which an attempt is made to regulate the content of CO 2 in outdoor and indoor air, is the ABOK standard "Residential and public buildings. Norms of air exchange. " As the recommended reference, the maximum permissible concentration in outdoor air is suggested: rural area - 332 ppm (650 mg / m 3), small cities - 409ppm (800 mg / m 3), large cities - 511ppm (1,000 mg / m 3). The upper permissible limit of CO 2 concentration in residential and public buildings should not exceed the concentration in the outside air by 638ppm (1250 mg / m 3). In this case, the required air exchange per person is 28 m 3 / h.

Finnish scientists under the leadership ofOlliSeppanen conducted 21 experiments on the basis of more than 30 000 subjects to study the effect of the concentration of carbon dioxide. If the level of carbon dioxide in the office space was below 800ppm (0,08% by volume), such symptoms as inflammation of the eyes, nasal congestion, nasopharyngeal inflammation, problems associated with the respiratory system, headache, fatigue and difficulty with the concentration of attention that employees experienced at a higher CO 2 concentration , significantly decreased.

This spring, I measured the level of CO 2 in the premises of the conditioning department, with the central air conditioner running, with an air exchange rate of about two. It was from 750 to 920ppm. With an external concentration of 680ppm. Lomonosov Street is always loaded with transport.

1. GOST 8050-85. Carbon dioxide is gaseous and liquid. Technical conditions.

2. Standard   EN 13779: 2004. Ventilation for non-residential buildings - Performance requirements for ventilation and room-conditioning systems.

3. Hygienic standards of GN 2.2.5.2100-06. The maximum permissible concentration (MPC) of harmful substances in the air of the working area (Supplement No. 2 to GN 2.2.5.1313-03. The maximum permissible concentration (MPC) of harmful substances in the air of the working area).

4. SanPiN 2.2.3.570-96. Hygienic requirements for coal industry enterprises and organization of work.

5. SNiP 41-01-2003. Heating, ventilation and air conditioning.

6. SanPiN 2.1.2.1002-00. Sanitary and epidemiological requirements for residential buildings and premises.

7. SP 2.5.1198-03. Sanitary rules for the organization of Passenger traffic.

8. ABOK STANDARD - 1 2002. Residential and public buildings. Norms of air exchange. - Moscow: AVOK-PRESS, 2002.

9. Olli Seppanen. Energy-efficient ventilation systems to ensure a high-quality microclimate of premises // AVOK. - 2000. - № 5.

10. Ole Fanger P. The quality of indoor air in buildings built in a cold climate, and its impact on health, training and productivity of people's work / / ABOK. - 2006. - No. 2.

I.V. Gurina

The modern person is almost 90% of the time in the room. The mothers are sent to the kindergarten, where groups are often crowded, students and students sit in classrooms for 40 people or more, and adults spend much longer than eight hours a day in the workplace. When you enter a room where there are a lot of people, you almost always feel that it's harder to breathe there than outside. I want to say "not enough oxygen". This is not true. In fact, oxygen is still more than enough, but the concentration of carbon dioxide has increased in the room. What happens in this case with our body? How harmful is it? Modern research proves that the increased content of CO 2 in inhaled air negatively affects blood, mucous membranes, respiratory and urinary systems, bone tissue, immunity and mental activity of a person.

Figures

It is best to breathe in nature. In pure country air, 380-400 ppm of carbon dioxide, that is, 0.038-0.04%. These concentrations are optimal for human respiration

The content of carbon dioxide in the air for the past 50 years has increased by 20% and is constantly growing - especially in large cities due to car exhausts and industrial emissions. Today, the level of CO 2 in the air of a large city can be 600 ppm (0.06%) or higher. We will not discuss the atmosphere in detail: it is important for us that this happens in the premises where we spend almost all the time. Closed rooms are a kind of CO 2 trap. Air with already elevated or even normal content of carbon dioxide comes through windows and ventilation, and then its concentration begins to grow rapidly due to the breathing of people who are in the building. There are aggravating circumstances here: forced ventilation may not be at all or it works poorly, and the natural one does not work, because the plastic windows do not let in air and they are closed so that no one gets a cold.

Indoors, the level of carbon dioxide rises much faster than oxygen decreases. Measurements show that, even when the CO 2 level in the school class reaches 1000 ppm (0.1%), the oxygen content remains practically unchanged (Fig. 1).

Of course, the increase in carbon dioxide depends on the number of people in this room, on their weight and what they do. The gym will become stifling much faster than in the office (Table 1).

Researchers know that there is a connection between the concentration of CO 2 and the sensation of stuffiness. A person begins to feel the symptoms of "lack of fresh air" (and in fact an increased concentration of carbon dioxide) already at its level of 0.08%, that is, 800 ppm. However, in modern offices there are also 2000 ppm CO 2 and higher. But more on that later.

What is acidosis and why is it bad?

Normally, the acidity (pH) of a person's blood is approximately 7.4. Our body is tuned to this figure, it is necessary for the work of all the enzyme and biological systems of the body. It is logical to assume that even small constant changes in the acidity of blood can have a very strong effect on a living being.

What happens when an increase in the concentration of CO 2 in the air that enters the body? The partial pressure of CO 2 in our alveoli increases, its solubility in the blood rises, and a weak carbonic acid (CO 2 + H 2 O = H 2 CO 3) is formed, which in turn decomposes into H + and HCO 3 -. Blood is acidified, which is scientifically called acidosis. The higher the concentration of CO 2 in the air, which we constantly breathe, the lower the pH of the blood and the more acid reaction it has (Figure 2).

Minimal physiological consequences of acidosis are overexcitation, heart palpitations and a moderate increase in pressure. With a stronger acidosis, a person becomes sluggish, drowsy, and feels anxious. But all this happens already at the concentrations of carbon dioxide, typical for modern premises, where there are a lot of people. However, when a person goes to fresh air for a long time, his condition gradually comes back to normal.

And if you breathe air all your life, in which there is a lot of carbon dioxide, daily, for 20 hours and more? When acidosis occurs biochemical changes in the body, if it is chronic, then, apparently, they at some point may become irreversible. In what exactly - scientists have yet to find out.

For the constant concentration of hydrogen ions within the body, its buffer systems respond. In particular, a big role here is played by the kidneys, which deduce an excess of unnecessary substances. In addition, the body has inorganic buffers. Some of the most important are bicarbonate (NSO 3 -) and phosphates. There are other, organic, such as hemoglobin and plasma proteins. But still 53% of the total buffer capacity of the blood falls on the system "bicarbonate - СО 2" (the content of bicarbonate in the plasma is 24 mmol / l).

When acidosis begins, the body first defends itself, increasing the concentration of bicarbonate in the blood plasma, as evidenced by numerous biochemical studies. To compensate for acidosis, the kidneys intensively secrete H + and delay HCO 3 -. Strictly speaking, the concentration of CO 2, at which the increase in bicarbonate in the blood begins, could become one of the scientifically valid norms for the allowable content of carbon dioxide in the premises. Then other buffer systems are turned on, and the secondary biochemical reactions of the organism are much more complicated (we will not go into details in detail, the mechanism is rather complicated). Since weak acids, including carbon (H 2 CO 3), can form weakly soluble compounds (CaCO 3) with metal ions, they are deposited in the form of stones, primarily in the kidneys. Fortunately, a person spends in a stuffy place not all the time, so this process is reversible - after some time after entering the fresh air calcium carbonate should dissolve.

Karl Schafer, an employee of the Medical Research Laboratory of the US Navy Submarine Fleet, investigated how different concentrations of carbon dioxide affect guinea pigs. Rodents were kept for eight weeks at 0.5% CO 2 (oxygen was normal - 21%), after which they had significant calcification of the kidneys. It was noted even after prolonged exposure to guinea pigs of lower concentrations - 0.3% CO 2 (3000 ppm). But that is not all. Shafer and his colleagues found the demineralization of bones in the guinea pigs after eight weeks of exposure to 1% CO 2, as well as structural changes in the lungs. The researchers regarded these diseases as an adaptation of the body to the chronic effects of CO 2. If scientists gave the experimental animals enough time to recover (more than a month), then these signs disappeared. However, the researchers themselves say that further experiments are needed to establish how the lower concentrations of carbon dioxide will affect the mammal state and when the changes in their organisms become irreversible.

Other effects and sick building syndrome

Research scientists are not limited to acidosis. For example, a survey of 344 employees from 86 offices in Taipei City (Taiwan) showed that, even at a CO 2 level above 800 ppm (0.08%), they had a rise in oxidative stress markers, for example 8-OHdG (8-hydroxy-2-deoxy- guanosine), determined in urine. The content of markers is the higher, the longer a person is in a stuffy room. The same volatile organic compounds act on the human body, and they and carbon dioxide intensify each other's negative influence.

UES scientists checked how schoolchildren feel in a room with carbon dioxide concentration above 1000 ppm, or 0.1%. (There are almost two thirds of such classes in the West, and in quite prosperous countries - in Sweden, Norway, Denmark, France.) In medical and biological tests, the respiratory and allergic state of 547 schoolchildren aged 9 to 10 years was assessed. It turned out that children spending a lot of time in a room with a high level of CO 2 are 3.5 times more likely to have a dry cough and twice as many get sick with rhinitis.

Korean scientists also investigated the effect of CO 2 on asthmatics. The sample consists of 181 children under the age of 14 from 110 houses and apartments in Seoul. The rooms measured the level of substances considered to be the main pollutants of air: CO, NO, house dust mite allergens, cockroaches, mold spores and CO 2 spores. Scientists concluded that only increased concentrations of CO 2 increased asthma attacks in children. By the way, respiratory infections and asthma are considered the main diseases of schoolchildren.

If we recall the primary signs of acidosis, we will understand why sluggish and sleepy schoolchildren do not perceive new material. The problem of elevated levels of CO 2 is also characteristic of kindergartens, especially for bedrooms. Poor children ... Fortunately, schoolchildren every 45 minutes there is a change during which they are expelled from the classroom, and a quiet hour with closed windows is also not very long.

Where can I get to be an adult? In many institutions, forced ventilation works very poorly - this is the reason for the CO 2 off scale. We have already said that plastic windows isolate heat and sound well, but completely deprive the room of natural ventilation, turning it into a large cellophane bag. The level of carbon dioxide in this "package" is growing very rapidly.

There are buildings that are called sick in special literature, and people working there experience sick building syndrome (SBS). The syndrome has many manifestations: irritation of the mucous membranes, dry cough, headache, decreased efficiency, inflammation of the eyes, nasal congestion, difficulty concentrating. This problem is familiar to residents of the EEC, the United States, Canada and many other countries. Some researchers believe that it is carbon dioxide that is one of the main causes of the development of SBS and this syndrome appears already at its level above 800 - 1000 ppm. Why did they decide that the culprit was carbon dioxide? Because when in the office room its concentration dropped below 800 ppm (0.08%), then the symptoms of SBS became weaker. In addition, the level of impurities that could cause such symptoms grows much more slowly than the level of CO 2, as people constantly exhale it.

About the syndrome of the sick building began to speak after there were houses with good thermal insulation and tightly closed windows, as well as a low level of ventilation due to energy savings. Of course, the reasons for the SBZ can theoretically be the allocation of construction and finishing materials, substances that emit the human body, mold spores, etc. If ventilation in the room is poor, then certainly the concentration of these substances in the room will also increase, but more slowly, than СО 2. Carbon dioxide acts as a thin indicator - it indicates that the level of ventilation is insufficient, which means that the concentration of other pollutants will also grow.

English experts at Middlesex University (UK), after a thorough investigation involving 300 people, made a verdict: the carbon dioxide level in the office should not exceed 600-800 ppm (0.06-0.08%). If it is higher, then attention is reduced by 30%. At concentrations of CO2 above 1500 ppm, 79% of the respondents experienced a feeling of fatigue, and more than 2000 ppm - two-thirds of the subjects could not concentrate. In 97% of employees suffering from migraine, it appeared already at a carbon dioxide level of 1000 ppm (0.1%).

A scientist from the UK DS Robertson believes that people begin to feel the deterioration of air quality already at a CO2 concentration of 600 ppm, and not at 800, as mentioned at the beginning of the article. When it gets even higher, individual people have one or more classic symptoms of carbon dioxide poisoning - breathing problems, rapid pulse, headache, hearing loss, sweating, fatigue, physiological disorders, and all of them grow in direct proportion to the level of CO 2 (Table 1). 2, 3). According to other data, in 15-33% of people these symptoms occur at a concentration of 600-800 ppm, in 33-50% at 800-1000 ppm, and 100% will experience them at a concentration of 1500 ppm. The design model says that in order to maintain CO 2 in a room of 600 ppm, 68 m 3 of air per hour per person must be forced into it.

Table 2. Short-term and long-term effects on humans
   increased concentrations of carbon dioxide

How can we understand that this is the effect of CO 2, rather than other poisonous products formed in the process of human life (including acetone, ammonia, amines, phenols ...)? In the University of Budapest, technology and economics have developed a special methodology that allows to minimize the level of pollution by other substances. Confirmed that it is CO 2 that is to blame. The study involved young and healthy people, whose average age was 21 years, and, despite the fact that the experiments lasted no longer than 140-210 minutes (concentrations reached 3000 pgs), they felt frankly unimportant. What to say about employees who are in offices for eight to nine hours every day for many months and years.

In early 2009, Lawrence Berkeley National Laboratory staff (USA) tried to understand how carbon dioxide in concentrations of 550, 1000 and 2500 ppm affects mental activity and human health. The experimental procedure was similar to that used by Hungarian scientists, but volunteers participating in this experiment were at the given levels of CO 2 daily for eight hours for three months. The received data are still being processed, but the optimism is inspired by the fact that at last a clear standard of experiment has appeared.

Here is another important point: today the level of CO 2 concentration in the room is the main indicator of air quality. It acts as an indicator gas, through which it is possible to judge not only about other pollutants, but also about how well the ventilation system in the building works. Studies in the classroom showed that if in the air there are, in addition to carbon dioxide, volatile organic compounds and formaldehydes, then it is sufficient to monitor only CO2. If ventilation copes with it, the remaining pollutants also remain at a low level. Moreover, according to CO 2, one can also judge the amount of bacteria in the air. The more carbon dioxide, the worse the ventilation and the more air in the air of different bacteria and fungi. This is particularly noticeable in winter, when the intensity of ventilation decreases, and the number of respiratory infections increases.

Hidden problem

The problem of carbon dioxide in the room exists in all countries, but in Russia it seems to be like no. Build new buildings, often with the use of modern "green" technologies, old buildings modernize, put new windows. And people are uncomfortable, and the population of large cities as a whole is weaker and more sick. Doctors treat the consequences, sin on the general pollution of the atmosphere, and there are no strict norms for the maintenance of carbon dioxide in the premises in Russia.

Table 3. How different amounts of carbon dioxide in the air affect a person

For the last several decades, Russian studies on this subject have hardly appeared. Meanwhile, some measurements at Moscow offices showed that in some of them the CO 2 level is 2000 ppm and higher. In the sixties of the last century OV Eliseeva in her thesis carried out detailed studies on the substantiation of MPC of СО 2 in the air of residential and public buildings. She tested how carbon dioxide affects concentrations of 0.1% (1000 ppm) and 0.5% (5,000 ppm) on the human body, and concluded that short-term inhalation of carbon dioxide at healthy levels by healthy people causes clear shifts in the function external respiration, blood circulation and electrical activity of the brain. According to her recommendations, the content of CO 2 in residential and public buildings should not exceed 0.1% (1000 ppm), and the average CO 2 content should be about 0.05% (500 ppm). Despite the fact that even a short-term effect caused an undesirable effect, neither the MPC nor any other standards for carbon dioxide at that time were adopted in the USSR. There are no such norms for educational, office and residential premises in SNiPs (building codes) and SanPinas ( sanitary rules  and norms).

In Europe, the USA and Canada, as a rule, 1000 ppm (0.1%) is considered the norm. It is in accordance with these figures that the ventilation of buildings is calculated. Many schools monitor air quality by the level of carbon dioxide. Of course, this level does not always and not always correspond to the norm. But in this case, the school administration is obliged to take measures to improve the situation. In Finland, for example, a school in which classes an increased level of carbon dioxide is detected may even be closed until ventilation is established.

In general, in the West, the topic of indoor air quality is quite popular. Annually conferences are held on the topic "Healthy building" and the topic of ventilation there rises constantly. By the way, about ventilation systems. On the one hand, in the modern world, everyone is trying to save electricity, on the other - you need to maintain good air exchange, and this requires a large amount of electrical energy. In Finland, scientists proposed to remove carbon dioxide with the help of absorbers built into ventilation systems. Thus, it may be possible to achieve a reasonable balance between energy savings and a safe level of carbon dioxide in the premises. Such household absorbers of carbon dioxide for premises already exist, it would be the desire to apply them.

In recent years, projects of so-called green buildings have appeared in the USA and in Europe. They are built of environmentally friendly materials and should consume as little energy as possible or provide it themselves. Everything would be fine, but this inevitably leads to savings on ventilation. In December 2008, the British Daily Mail reported on how Professor Derek Clements-Krum investigated several schools that were trying to implement the idea of ​​an environmentally friendly building with minimal energy consumption. In these schools, the professor recorded a very high level of CO 2 in the classrooms. As a result, the children were inhibited by the thought process, they were sluggish and could not normally learn.

There was information that the first "green" high-rise administrative and residential complex "Kristall" (187 thousand m 2) will also be built in the north-east of Moscow. If we consider that few people are familiar with the problem of carbon dioxide in a room in Russia, the health of people who will be in this building causes fears in advance.

In our school classes, forced ventilation is practically non-existent. Teachers should do "through ventilation" of the class during the change. True, it is cold in winter, and this is impossible. Even after airing, the level of carbon dioxide quickly grows several times, so by the middle of the lesson, children can not concentrate. In modern office buildings there is ventilation, but often in the construction of buildings count on a single number of workers, and then they are much more. By the way, if in the street CO 2 becomes at some point very much, then we can not do without and without carbon dioxide absorbers.

In recent years, accurate infrared sensors have appeared to measure the level of carbon dioxide in the premises. They are part of gas analyzers and show the concentration of carbon dioxide in real time, so they are convenient to put in residential and public buildings, schools and kindergartens. However, in order to benefit from these measurements, clear standards for the level of carbon dioxide in the premises are needed. And we do not have them yet.