The zero gas generator provides clean and dry zero-level air. It is mainly applied to zero calibration of ambient air quality monitoring system or analyzer. It can also be used as flushing gas in permeation tube & furnace and oxidant gas for FID analyzer. Zero gas generator includes external oil-free air compressor, pressure and flow controller, water removal system. Based on adsorption, filter, reaction and other principles, the removers can remove So2, NO, No2, O3, H2S, CO, Nh3, hydrocarbon, particulate matter and output dry and clean air as well. The water removal system inside the analyzer could remove the moisture in the air. The dew point of produced air is lower than -20℃ and it is not effected by the inlet dew point. It contributes to removal of other gases as well as greatly extending servicelife of other chemical removal.