Gas-phase filter: The gas-phase filter is a method of using specialized filter media. Moreover, chemical substances are also used here to eliminate gaseous impurities from the air. Most of the Gas-phase filters use a substance called sorbent. It is used to absorb chemical substances. It also distant chemicals from the inside air. However, the Gas-phase filter works under two processes. It removes gasses both physically and chemically. It follows both absorption and chemisorptions.