Clean air delivery rate

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.

The CADR ratings were developed by the 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[1] and the Federal Trade Commission.

Any device or technology that removes particulate matter from the air can be tested for CADR numbers.

[2] The CADR numbers reflect particulate matter remaining in the air, which has not been captured by the filter or other technology.

Due to the measurement process, the CADR rating is intended for use only with equipment designed for residential spaces.

The AHAM seal (usually found on the back of an air cleaner's box) lists three CADR numbers, one each for smoke, pollen, and dust.

If the filtering unit does not mix the test room's air very well, it may receive a lower CADR measurement because it does not operate as efficiently as it should.

So CADR ratings for dust and pollen come out lower than would be expected by looking only at the filter's efficiency at removing large particles.

A filter that is very good at removing smoke particles by using a slow fan or electrostatic effects will not get as good CADR numbers for pollen and dust because those particles will fall down and deposit on room surfaces during the test, before the filter has had a chance to collect them.

Known as ANSI/AHAM AC-1, it measures the air cleaner's ability to reduce tobacco smoke, dust and pollen particles in a room.