Clean Air Delivery Rate

Clean Air Delivery Rate (CADR) is a figure of merit that is the cubic feet per minute (CFM) of air that has had all the particles of a given size distribution removed. For air filters that have air flowing through them, it is the fraction of particles (of a particular size distribution) that have been removed from the air, multiplied by the air flow rate (in CFM) through the device. More precisely, it is the CFM of air in a 1,008-cubic-foot (28.5 m3) room that has had all the particles of a given size distribution removed from the air, over and above the rate at which the particles are naturally falling out of the air. Different filters have different abilities to remove different particle distributions, so three CADR's for a given device are typically measured: smoke, pollen, and dust. By combining the amount of airflow and particle removal efficiency, consumers are less likely to be misled by a high efficiency filter that is filtering a small amount of air, or by a high volume of air that is not being filtered very well. Clean Air Delivery Rate (CADR) is a figure of merit that is the cubic feet per minute (CFM) of air that has had all the particles of a given size distribution removed. For air filters that have air flowing through them, it is the fraction of particles (of a particular size distribution) that have been removed from the air, multiplied by the air flow rate (in CFM) through the device. More precisely, it is the CFM of air in a 1,008-cubic-foot (28.5 m3) room that has had all the particles of a given size distribution removed from the air, over and above the rate at which the particles are naturally falling out of the air. Different filters have different abilities to remove different particle distributions, so three CADR's for a given device are typically measured: smoke, pollen, and dust. By combining the amount of airflow and particle removal efficiency, consumers are less likely to be misled by a high efficiency filter that is filtering a small amount of air, or by a high volume of air that is not being filtered very well. The CADR ratings were developed by Association of Home Appliance Manufacturers (AHAM) and are measured according to a procedure specified by ANSI/AHAM AC-1. The ratings are recognized by retailers, manufacturers, standards organizations, and government bodies such as the EPA and the Federal Trade Commission. Whole house air cleaners are not covered by the CADR specification because the measurement is performed in a standard 1,008-cubic-foot (28.5 m3) room, the size of a typical house room, which has different airflow patterns than whole-house filters. Measurements are made with the filter running and not running, so particles that naturally fall out of the air are not being counted as part of filter's operation. The measurement only applies to particulate matter, not to gases. Any device or technology that removes particulate matter from the air can be tested for CADR numbers. Anyone with the necessary equipment can perform the ANSI/AHAM AC-1 measurements. The AHAM performs the tests for manufacturers who are paid members of AHAM which choose to use their service, allowing the manufacturer to display a seal that certifies AHAM performed the test. The CADR numbers reflect particulate matter remaining in the air, which has not been captured by the filter or other technology. Some low-efficiency filters employ ionization, which attaches a weak electrostatic charge to particulate matter, which can cause several smaller particles to group together resulting in a lower particle measurement count. Ionization can also cause particulate matter to attach to surfaces such as walls, and flooring, resulting in lower particulate counts in the air, but without having particulate matter permanently removed from the air.