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The CADR Rating

CADR stands for Clean Air Delivery Rate. In general, this numerical value will show you exactly how much of the specific particles to be removed from the air. In other words, CADR rating indicates how fast the air purifier can clean the air within a particular size room. For example, an air purifier with CADR rating of 300 cfm will clean a room of 300 sq ft much faster than an air purifier with CADR rating of only 200 cfm. CADR rating is taken in CFM which stands for cubic feet per minute, or in m³/hour. CADR measurement is usually for pollen, smoke, and dust. These three pollutants are not only small in size but also the most unwanted particles in the air. Smoke particles are ultra-fine particles, with the defined particle size ranges from 0.1 to 0.3 microns. Dust particles are common particles with size from 0.5 to 3 microns. And pollen particles are the large particles that you can see with your own eyes, with size from 5 to 11 microns. CADR ratings are invented by AHAM (Association of Home Appliance Manufacturers).


CADR ratings are strictly determined by an ANSI/AHAM AC-1 test. This test is simple to understand. The testing agency will put the testing air purifier unit into a chamber with a determined amount of contaminants. After 20 minutes of running, they stop the air purifier and measure the air in this chamber one again. Finally, they can make conclusion of the CADR ratings for this air purifier.

However, this test has its own limits. CADR ratings is only for the specific contaminants and in this case, dust, pollen and smoke. If you need an air purifier for a specific kinds of virus or bacteria, AHAM’s CADR ratings just are not useful. Also, the elapsed time of 20 minutes is a clear limit of this test, as some air purifiers are working fine for the first 20 minutes and degrade in performance over time.

Also, if an air purifier uses employs an ionizer it will cause false readings in the CADR test. Ionization is a process of sticking many small particles into a bigger one, but not trapping them. Usually these bigger formed particles are dropped on the floor and wall. Without proper removal or absorption, these pollutant particles are ready to be in the airborne once again.

We at Austin do not give much credence to the CADR rating as the test lasts for a very short period of time (20 minutes) and tests for dust, pollen and smoke. Since many less expensive air cleaners have built machines to beat the test (post a good showing for 20 to 30 minutes) we feel the consumer is being cheated. What really matters during the lifetime of the air purifier is filter composition and volume. Austin Air Purifiers contain more media and are more comprehensive media than any competitor on the market today.

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