As far as the ionization chamber is concerned, the emission of the high subordinal impurity in the wall material of the ionization chamber is the main source of the ionization chamber's own background. Radioactive contamination of ionization chamber materials has been noted in early work. The main measures to reduce the effect of chamber wall emission in atmospheric ionization chambers are as follows:1) Increase the ionization chamber volume,2) Change the ionization chamber into a negatively charged gas