A widely used measure for room air purifier performance is CADR, or Clean Air Delivery Rate, a metric developed by the Association of Home Appliance Manufacturers (AHAM). CADR is a measure of the speed with which a unit removes a target pollutant such as dust. The higher the CADR, the better.
The ENERGY STAR specification uses a CADR-to-Watt ratio to measure energy efficiency using the CADR for dust. ENERGY STAR certified room air cleaners must produce a minimum 2.0 CADR/Watt for dust. The U.S. EPA does not endorse any manufacturer claims of healthier indoor air from the use of air purification products.