Zeolite molecular sieves have a strong separation effect on nitrogen and oxygen. It has the structure and characteristics of a crystal, the surface is a solid skeleton, and the internal cavities can play the role of adsorbing molecules. There are pores connected to each other between the cavities, and molecules pass through the pores. Due to the clean nature of the pores, the pore size distribution of the molecular sieve is very uniform. Molecular sieves selectively adsorb molecules based on the size of inside their crystals, that is, adsorb molecules of a certain size while repelling molecules of larger substances.