Static distribution and characteristics of standard gas

 In air and waste gas monitoring in environmental monitoring, standard gases are as important as standard solutions and standard substances, and are the basis for testing and testing methods, evaluating sampling efficiency, drawing standard curves, calibrating analytical instruments and conducting testing quality control. The method of preparing low-concentration standard gas is usually divided into: static gas distribution method and dynamic gas distribution method.

The static gas distribution method is to add a certain amount of gaseous or vaporous raw material gas into a container of known volume, then fill it with diluent gas, and mix it. The concentration of the standard gas is calculated according to the amount of the dilution gas added to the raw gas and the volume of the container. The raw gas used can be pure gas or mixed gas with known concentration, and its purity needs to be determined by suitable analytical methods.

The advantages of the static gas distribution method are that the equipment used is simple and the operation is easy. However, due to the active chemical properties of some gases, chemical reactions may occur in contact with the container wall for a long time. Its concentration changes with the placement time, especially the preparation of low-concentration standard gas, which often causes large errors. For standard gases that are chemically inactive and not used in large amounts, this method is relatively simple to prepare.