Gas Detection Technology Methods

　　At present, there are more than 100 kinds of atmospheric pollutants that have been recognized. These pollutants exist in the ten major gases in the form of molecules and particles. The main molecular pollutants are C02, 502, NOX, CO, 03, total oxidants, halogenated hydrocarbons and hydrocarbons, and the main particulate pollutants are TSP, IP, natural dust, etc. The main chemical components are heavy metals and polycyclic aromatic hydrocarbons. In the atmospheric trace gas measurement technology, spectroscopy and various chemical methods are mainly used.

　　Gas chromatography has two functions: separation, enrichment and detection. It is widely used in the chemical and petroleum industries. Atmospheric samples are first separated and concentrated in a capillary column, and then the various gas components distilled are detected using a very sensitive hydrogen flame ionization detector or an electron capture detector (depending on the gas composition). Because it is the detection of pure gas samples after separation, the measurement results are highly reliable. The measurement results of many spectral methods are often compared with chromatographic results to determine the accuracy of their measurements and estimate the source of errors. In recent years, mass spectrometry combined with chemical ionization sources or ion-molecule reaction technology has reached very low detection limits and has been used to measure OH, HO2 and RO2 free radicals. Due to the fast response time of mass spectrometry, low-pressure chemical ionization source mass spectrometers have been used for real-time continuous monitoring of benzene, toluene, xylene and polycyclic aromatic hydrocarbons in ambient air. If the gas sample after chromatographic separation and enrichment directly enters the ionization chamber of the mass spectrometer for mass spectrometry identification and measurement, this is the chromatography-mass spectrometry technology. This technology combines the separation and enrichment functions of chromatography with the fingerprint characteristics of mass spectrometry identification, and has become one of the most sensitive and specific measurement technologies. Chromatography takes a certain amount of time to separate and enrich in the chromatographic column, so it is difficult to monitor in real time, which is a defect of chromatographic monitoring.

　　The gas detection tube is a long and thin glass tube with a scale printed on its outer surface, which can easily and directly read the concentration of the gas (vapor) being measured. The detection tube contains fillers such as silica gel or alumina, and highly selective and highly stable detection reagents are attached to it. When the target gas and the detection agent come into contact, a chemical change will occur, resulting in a noticeable color change. Both ends of the detection tube are burned and sealed.

　　To date, more than 600 gases can be detected using this method.

　　Features: Simple operation: Anyone can complete the test quickly at any time and any place.

　　Intuitive judgment: After the vacuum is completed, the concentration value can be directly read from the scale corresponding to the color-changing layer, which is simple and clear.

　　Wide detection range: The detection range can be expanded by adjusting the air extraction volume.

　　Accurate test results: Each batch of test tubes must be calibrated through multiple tests to ensure the accuracy of the test. Each test tube is marked with a quality inspection batch number.

　　Long shelf life: The product has good stability and a long shelf life.

　　The manual gas collector used with it has a volume of 100ml and weighs only 240g. This device is only suitable for rapid gas detection tubes.