There are three methods for standard gas distribution:

1. Syringe gas distribution method

When only a small amount of standard gas is needed, a 100ML syringe can be used to prepare the standard gas; after multiple dilutions, the required low-concentration standard gas can be obtained. Although the syringe gas distribution method is simple and easy to implement, due to the adsorption of the inner wall of the syringe, large dead volume and incomplete liquid volatilization, the concentration of the prepared gas has a large error.

2. Plastic bag gas distribution method

In this method, a plastic bag is used as a container. When using plastic bags for gas distribution, special attention should be paid to preventing the adsorption of gas on the bag wall. Teflon bags, polyester resin plastic bags and polyethylene film aluminum foil sandwich bags are usually used for air distribution.

3. Gas distribution method for high-pressure steel cylinders

This gas distribution method uses high-pressure steel cylinders as containers to prepare a mixture with a higher pressure. According to the gas distribution measurement method, it is divided into pressure method, flow method, volume method and mass method. Among them, the concentration of standard gas prepared by mass method is the most accurate.