Point of Contention: CADR and Efficiency Among Air Purifier Manufacturers

Air Purifier Clean Air Delivery RateOn many different brands of air purifiers you will find the Association of Home Appliance Manufacturers (AHAM) certified Clean Air Delivery Rate (CADR) logo. This certification is recognized by the American National Standards Institute (ANSI) and used by the Consumer Union in rating air purifiers for their Consumer ReportsŪ publication. A complete list of AHAM certified manufacturers can be found on their website. There are no surprises when it comes to this list unless we note who is absent. Some of the most prominent air purifier manufacturers are not members nor do they submit their products to AHAM testing. In trying to better understand who is absent and why, it would be helpful to better explain CADR and AHAM's role in the air purifier industry.

Developed in the early 1980's CADR is a measure of the removal of specific particulates in a controlled environment. The ability to filter smoke, dust and pollen particles ranging from 0.10 to 11 microns is measured. CADR and the testing procedures are approved and accepted by ANSI, which lends a good deal of veracity to the certification. So with the stated purpose being to measure "the rate of contaminant reduction" why would certain manufacturers refuse to submit to this testing standard?

Air Purifier CADR CertificateWhile AHAM created this independently certified measure, what CADR actually tells us is not necessarily helpful. The CADR does not take into account factors such as the ability to neutralize and/or remove Volatile Organic Compounds (VOC's), germs, bacteria, or viruses, nor does it provide any information as to the durability or long term efficiency of the air purifier being tested. Units tested that employ an electrostatic charge often dramatically drop in efficiency after a relatively short period of time. As the filter fills, the ability to attract and trap new particles diminishes, yet CADR testing measures are not long enough to provide this sort of information. While electrostatic precipitators units traditionally rate well with the CADR they also emit the harmful lung irritant, ozone. The size of the particulate filtered in the test is also somewhat problematic. Many of your most harmful particles are by far smaller than 11 microns. The wide size range of particulate filtered in the CADR test cannot necessarily provide useful information about filtration at the submicron level. Simply put, most testing regarding larger particles will result in a higher efficiency rating; the larger the particle, the easier it is to trap. For smaller particulate, the DOP (dioctyl phthalate)Test would yield much more conclusive results as to the efficiency of a given filter to collect and trap particles as small as 0.30 microns.

The CADR was developed by AHAM, a trade association formed by manufacturers, and membership to AHAM is voluntary but not without cost. Manufacturers can gain CADR certification without membership to AHAM, but fact that AHAM is by origin a trade association, with paying members, casts an uneasy shadow on the CADR certification, despite its acceptance by ANSI. One organization attempting to balance the interests of its dues paying members with creating and using a product performance test is problematic for some manufacturers. Further, there is little incentive for an independent manufacturer to submit its product to a test that does not necessarily measure some of its most valuable features. An overriding concern is the basic need for the most accurate evaluation of efficiency, and AHAM's Clean Air Delivery Rate does not necessarily provide this.

While CADR is a measurable performance indicator by which consumers and retailers can compare air purifiers, it should not be the lone determining factor in choosing a product. In addition to CADR, reputation, cost, additional features, true HEPA filtration, the use of activated carbon, and ease of use all should be considered and weighed against a customer's individual needs.

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