CADR is an established standard rating by the independent Association of Home Appliance Manufacturers (AHAM) in USA. It measures the efficiency of for all air purifier according to a recognized standard. It take into an account of room size and the volume of clean air produced per minute or hour. In USA, the CADR of dust, pollen and smoke, which are the three most common indoor air pollutants, is rated.  In China, more strictly, apart from the PM2.5 and/or PM10, the removal of the Total Volatile Organic Compounds, Formaldehyde, Toluene, Ammonia, airborne bacteria, virus, allergen will also be rated.