Chemical filters usually use activated carbon, modified activated carbon, alumina, ion exchange resin and other purification media, and apply physical adsorption, chemical adsorption (oxidation, medium core, Ion exchange, catalysis) and other principles to effectively purify gaseous molecular pollutants and reduce the concentration of pollutants. Common adsorption media are activated carbon, modified activated carbon, alumina (impregnated with potassium permanganate), ion exchange resin. Activated carbon: for VOCs volatile organic compounds; Modified activated carbon: for acid/alkaline gas and other special gases; Alumina (potassium permanganate impregnation): for sulfur/nitrogen compounds, formaldehyde, ethylene and other gases; Ion exchange resin: for ammonia organic matter;