To determine the concentration of harmful substances, you must first take samples of atmospheric air. This process is extremely important and painstaking. This is due to the fact that even with the most accurate analysis, the results of incorrectly performed air sampling are distorted. Therefore, there are a number of requirements for this process:
- you need to get a sample that corresponds to the actual composition of the air;
- accumulate the required amount of the desired substance in the sample so that it can be detected in the laboratory.
Air sampling depends on several factors:
- aggregate state of the desired substance in the environment (condensation aerosol, gas, steam);
- possible chemical interactions of the desired substance with the surrounding atmospheric environment;
- amount of substances in the air;
- research method.
During research in the laboratory, variousair sampling methods. The most common are aspiration and sampling into the vessel.
Aspiration method
This is the most common way in hygienic practice. The peculiarity of this technique is aspiration. In other words, this is the filtration of the examined air with the help of special substances that are able to absorb a certain ingredient from all passing through it. This substance is called an absorbent medium. Disadvantages of the aspiration air sampling method:
- This is a very laborious process.
- Takes a long time (about 30 minutes). During this period, averaging of the concentration of a toxic substance can occur. And the concentration of the desired substances in the air changes too quickly. The air sampling technique is carried out by professionals.
Selection into vessels
This method is notable for its speed. It is used when it is limited to a small volume of the studied air and there is no need to accumulate the desired substance in the sample. In this selection, various containers and vessels are used: cylinders, bottles, syringes and gas pipettes, as well as rubber chambers. This air sampling technique is very sensitive and accurate.
Several types of aspirators are used in practice. The simplest among them is water. This air sampler consists of a pair of identical glass bottles that are pre-calibrated. These vessels hold about 3-6 liters, closestoppers, from which two glass tubes emerge. One of them is long and reaches the bottom of the bottle, the other is short, ending just below the cork. The long tubes of a pair of bottles are connected by a rubber tube with a clamp. An absorber is attached to the short one. When the clamp is opened, water flows into an empty vessel located above the one that originally contained the liquid. At this time, a rarefaction occurs above the water surface, due to which the air under study is sucked through the absorber. The rate of such suction is from 0.5 to 2 liters per minute, and the volume of air that has passed through the absorber is the same as the amount of water that has passed from the top bottle to the bottom one.
This method is time consuming and one of the most difficult. The Migunov electric aspirator is considered convenient for use. This device combined an electric blower with rheometers, which are glass rotameter tubes, two of which are needed to measure the speed of air extraction, and the other two are designed for high speed. The low speed is from 0.1 to 1 l / min, the high one is from one to 20 liters per minute. The lower part of the rotameters is connected to fittings brought to the front of the device. Rubber tubes are attached to these fittings along with absorption devices. Thanks to this scheme, four samples can be taken at the same time. The upper part of the rotameter has valve handles, which are similarly brought out to the front. This helps regulate the rate of air sampling.
The principle of operation of thisThe device consists in the fact that during the connection to the network, the blower rotor rotates with the help of an electric motor. At the same time, the pressure in her body decreases. And the air placed outside the device passes through the fittings. Then it goes outside. Knowing the time spent on its passage through the aspirator and its speed, you can determine the volume of air passing through the absorption device, which is attached to the fitting.
Existing absorbers are designed to take chemical impurities from the air using solid and liquid media. Both the absorber and the medium for it are not chosen by chance. Here, the aggregate states of substances that are being studied are taken into account. As well as the need to ensure prolonged contact of the substance itself and the absorption medium.
If the investigated gas or vaporous substance is in the air in large quantities, if the method of its determination is very sensitive, then, accordingly, small volumes of the analyzed air are needed. This requires one-shot sampling methods. For them, rubber chambers, calibrated bottles and vessels containing from 1 to 5 liters, as well as gas pipettes of 100-500 ml are used. However, rubber chambers can only be used if the test substance does not exactly react with rubber. They do not retain air for more than three hours. It is pumped there with the help of a bicycle pump. For research, air is transferred to a calibration bottle or other absorber with the appropriate medium.
Selectionexchange method
When gas pipettes and bottles are filled with test air, this method is called the exchange method.
Air that can be tested in a laboratory is blown through a pipette or bottle many times. The pipette is filled with a rubber bulb, a pump. This is possible with open clamps or taps, if any. At the end of sampling, they are closed. If a calibration bottle is used, it is equipped with stoppers and two glass tubes. Rubber tubes with clamps are attached to their outer ends. Before starting the selection, the clamps are removed. And a pump or a rubber bulb is attached to one of the tubes. The bottle is then purged with test air many times. At the end of sampling, the tubes are closed with clamps.
Vacuum method
Indoor air samples are taken using a thick-walled calibration bottle. It is needed to create a vacuum in it using a special Komovsky pump. The air to be tested is sucked out of the bottle to a residual pressure that ranges from 10 to 15 mm Hg. Then you need to close the clamp on the rubber tube. Disconnect the vessel from the pump. And insert a glass rod into the end of the rubber tube. At the sampling site, the container is opened. It will quickly fill with air due to the equal pressure. At the end of sampling, the clamp is screwed down, and a glass stick is placed in place of the hole in the rubber tube.
Pouring method
Air sampling is done with a gas pipette or calibration bottle. They are filled with a special liquid,which should not react with the test substance and, moreover, dissolve it. For these purposes, plain water is often used. In cases where this option is excluded, resort to the use of saturated (hypertonic) solutions of sodium or calcium chloride.
The liquid is poured into the sampling site, and the vessel is filled with the test air. Then the rubber tubes are closed with special clamps, and glass sticks are placed at the ends, or simply both taps on the gas pipette are closed.
Sanitary tests
These samples are collected for chemical analysis and determine the total dust content in the human breathing zone and one and a half meters above.
Studying air pollution due to emissions from industrial enterprises, determine the average daily and maximum one-time concentration of harmful substances in the atmosphere. Sanitary air samples are usually taken at the time of greatest pollution on the windy side of the source. Take a minimum of ten samples at all points and at regular intervals. Atmospheric air sampling lasts about twenty minutes. If the distance from the source of pollution is increased (no more than five kilometers, further accurate analysis is simply impossible), the duration also increases to 40 minutes.
In order to identify radioactive and carcinogenic substances, it is necessary to suck a large amount of air through the filters. Because in populated areas, the studied elements are contained in negligible amounts. During samplingair in large industrial plants for research on the content of toxic substances (such as gases, vapors) or large amounts of dust, an important place is occupied by the sampling point. In industrial premises or buildings, pollutants are unevenly distributed. The air environment is constantly and chaotically mobile. For these reasons, instruments for sampling the atmosphere are located in the place where the work process takes place, at the level of one and a half meters from the floor. This is considered the breathing level of the workers. Three samples are taken per shift: at the beginning, middle and end of the working day. During their taking, the humidity, as well as the air temperature in the room, must be taken into account. Absorption devices, which are needed to take air samples in industrial plants, resemble glass test tubes that are sealed at the top and fastened with a pair of glass tubes. The test air enters through a long tube. And through the short one, it passes further to the blower through the rheometer. The lower part of the absorber is intended for the absorbed liquid, through which the test gas must be sucked. Air sampling of the working area is necessary for the normal functioning of the enterprise and ensuring working conditions for the team. In accordance with current legislation and labor protection requirements, this is a mandatory process.
Gravity selection method
This method of sampling indoor or outdoor air is based on the fact that dense particles that are suspended in it settle under the influence of gravity. The Durham Sampler is the main instrument thatused for gravity sampling of the air. The essence of his work is as follows. A special glass slide is inserted into the holder of the device, which is covered with glycerin gel. Then it is left in the air for a day. Particles that are carried by the air stream settle on the glass slide. Further, under laboratory conditions, the composition and number of particles are determined under a microscope. The results are presented as the number of particles that settled per square centimeter per day. Gravity air sampling is inexpensive and fairly simple, but it also has its drawbacks:
- Analysis results may be inaccurate due to factors such as wind direction, wind speed, precipitation and air humidity;
- a small amount of particles has time to settle in a day;
- large particles mostly fall on the slide;
- samples are collected by professionals, for this they need special devices, as well as aspirators for air sampling.
Volumemetric method
The essence of this method lies in the fact that particles that are suspended in the air linger on the obstacles set by its flows. Air samples in heavy industries should be collected at least once a year. Under the conditions of this method, the following samplers are used:
- Rotary. Its collecting surface is covered with a special substance, then it rotates for a certain time at the desired speed. The result of a test using this instrument is expressed asthe number of particles that have time to settle per day on one square centimeter. This method eliminates the influence of wind direction and speed on the analysis result, thereby providing a more accurate analysis. The Academy of Allergists and Immunologists recommends using such a device to detect harmful substances in the air.
- The aspirating sampler can pass the test air through a membrane filter with a given pore diameter. The collecting surface is needed in order for particles of a certain size to settle on it. This principle is key to the Bouchard spore trap, where the collecting surface can move at a speed of about 2 millimeters per hour. This makes it possible to monitor how the concentration of particles in the test air changes. The device has a weather vane, and therefore the direction of the wind does not affect the final results.
Evaluation of the results of the gravity sampling method allows to detect large particles (for example, ragweed pollen). For scientific purposes, more powerful and accurate volumetric methods are used.
Pollution research
Air sampling takes place in accordance with applicable law. GOST 17.2.3.01-86 is necessary for the correct analysis and calculation of errors.
In order to study the degree of air pollution in the Russian Federation, a special term has been developed - "maximum permissible concentration". To date, the maximum allowable standards have been determined. Concentration inthe air environment of harmful substances should be no more than five hundred substances. Air samples allow you to control the situation.
The maximum permissible admixture is considered to be the most concentrated admixture of atmospheric air, which refers to a certain period of time and periodically or throughout a person’s life will not have a harmful effect on him (even long-term consequences are taken into account) or on the environment.
In the case of a high concentration of gases, an air breakdown is carried out, the voltage in this case is about 33 kV / cm. As the pressure increases, so does the voltage.
There are laboratories, research institutes and individual qualified specialists who, using modern instruments and high-tech devices, determine and eliminate harmful substances located in houses, apartments, offices, land plots, etc. Air sampling is carried out by employees of sanitary and epidemiological stations, and further studies are carried out in the laboratory.
How to secure your home
If you begin to notice that one of your family members (or yourself) suffers from allergic reactions for unknown and invisible reasons, then you need to analyze indoor air samples. There are several ways to do this. Ordinary dust, mold, radon or various pathogens in the air adversely affect the he alth of people, especially young children. Atmospheric air sampling is necessary in case of allergic and other reactions in one of thefamily members. Methods to help analyze indoor air:
- Must install a carbon monoxide detector. This device plays an important role and literally saves lives. To install this small device, you only need an outlet. If the sensor emitted a warning sound, it means that the level of carbon monoxide in the apartment has changed. As you know, the gas has no color and almost no smell, and therefore the role of the sensor is really very great, it can save your life.
- Another way to keep your home safe is to test indoor air for radon. This is especially useful if the house is located near a concentration of uranium in the ground, which can lead to the accumulation of radon. In this case, air samples in the apartment must be carried out regularly. There are kits designed for chemical analysis of the content of radon in the atmosphere. They can be used on their own. Install and leave them for three days. After that, the kit is assembled and taken to the laboratory for analysis and a verdict.
- You can also buy air test kits for mold spores. To determine if there is a fungus or mold in the apartment, it is necessary to conduct a microbiological analysis of the air environment. Usually, this method is resorted to if someone in the family suffers from allergies or sinusitis. You can use the instruments for analysis yourself. However, you still need touse the services of the laboratory.
- At home, you can check for the presence of dust mites in the air. This phenomenon is present in almost all homes, especially private ones close to plantings and forests. However, if the concentration of ticks, bedbugs, fleas is too high, it is almost the same as toxic air. For laboratory analysis, a small vial is issued into which an air sample is placed and then sent to the laboratory for analysis and results.
After receiving the results, it is necessary to solve the corresponding problems. To eliminate them, there are special groups of people who work on call.
