The uniformity of VOC standard gases is a very important characteristic. Although various gases have high fluidity and diffusion ability, when preparing VOC standard gases, several component gases are sequentially filled into high-pressure steel cylinders, and the difference in molecular weight of each component gas results in uneven distribution of gas components in the cylinder, and some may even cause stratification. In addition, there is an adsorption and desorption equilibrium process between the gas components and the inner wall of the steel cylinder, which has an adverse effect on the uniformity of VOC standard gas components. Due to the above reasons, the preparation of VOC standard gas still requires certain mixing methods to solve the problem of uniformity of various component gases filled into steel cylinders. The cylinder rotation rolling method is a fast, simple, and effective method for solving the mixing of VOC standard gases. The natural diffusion method can also make the standard calibration gas mix evenly, but it takes a longer time to reach a uniform state. Wuhan ISOTOPE Technology Co., Ltd. Service hotline: 19526388246

The stability of calibration gases is also a very important basic characteristic. The stability of standard gas includes two aspects, namely the variation of standard calibration gas component content with time and the variation of standard calibration gas component content with pressure. Generally speaking, the stability assessment experiment for primary gas reference materials takes more than one year, while the stability assessment for secondary gas reference materials takes more than six months. Based on the experimental results, the validity period of the VOC standard gas, i.e. the validity period of the standard calibration gas, can be determined. The validity period of standard calibration gases cannot be arbitrarily given and must be based on the results of stability testing experiments. Maintaining long-term stability of component content in standard gas is extremely important. The material and inner wall treatment of standard calibration gas packaging containers are key factors affecting the stability of standard calibration gases.