CADR stands for Clean Air Delivery Rate. The AHAM (Association of Home Appliance Manufacturers) seal (usually found on the back of an air cleaner's box) will list three CADR numbers - one for tobacco smoke, one for pollen and one for dust. The CADR indicates volume of filtered air delivered by an air cleaner. The higher the tobacco smoke, pollen and dust numbers, the faster the unit filters the air. AHAM and independent testing laboratory verify CADR every year. Blueair model AV501 was awarded by AHAM for the highest CADR among similar models of air purifiers.