Most of the harmful substances in the production environment come from the exhaust gas and smoke in the process of industrial production. Air monitoring is necessary to understand the source and concentration of the pollutants. Air pollution detection includes sample collection and work analysis. The method of sample collection should be selected according to the purpose of monitoring, the state of the object in the air, the concentration and the sensitivity of the analytical method
the results measured by gas gathering method indicate the instantaneous concentration of harmful substances in the air. When the concentration of harmful substances is high or the sensitivity of the determination method is high, a small amount of air is enough for analysis, the gas gathering method is adopted. Gas gathering method is to collect air samples in a container and take them back to the laboratory for analysis. 1t is generally used to collect gas or vapor, which is not easy to be blocked by absorption liquid or adsorbent. Gas chromatography is often used to detect harmful substances in the air
the results measured by concentration method indicate the average concentration of harmful substances in the air in a normal time. When the concentration of harmful substances in the air is low, in order to meet the requirements of the analysis method, it is necessary to pass the field air through the collection tube containing absorption solution, adsorbent or filter paper, so that the air can be separated and concentrated, and then analyzed
the results measured by individual sampling method represent the average exposure concentration of workers in a working day, i.e. time weighted average concentration. The individual monitor relies on the diffusion or infiltration of the detected pollutant molecules in the monitor to complete the sampling process. 1t does not need pumping power and gas production measurement. After one working day’s exposure and sampling, the adsorbent is taken out, and the total amount of pollutants is detected by conventional analysis method after solvent elution. The result is the time weighted average concentration of one working day
Direct Reading detector is a variety of instruments made by chemical and physical methods, which can immediately indicate the concentration of harmful substances in the air on site. Some also have devices for recording concentration changes and alarming