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Is the AHAM CADR rating reliable when choosing an air purifier?

Image of IQAir HealthPro Plus home air purifier Would you like a reliable way to compare one air purifier to another? The AHAM CADR rating is one method used by some air purifier manufacturers to promote the value of their products.

But what is this CADR air purifier rating? Is it a reliable means to compare air purifiers? If so, why do so many top quality air purifier manufacturers not bother to get their units rated?

CADR, short for Clean Air Delivery Rate, was developed by the Association of Home Appliance Manufacturers as a means of providing air purifier ratings to consumers.

It should be noted that the manufacturers in this association are the very ones who determine what is to be tested, how it will be tested, and what is to be considered good performance. This is decided by a negotiated mutual agreement among the associated manufacturers.

Obviously, the air purifier manufacturers have a vested interest in creating a test their products will perform well in. Unfortunately, this conflict of interest has created a test with severe limitations.

Why is it misleading to compare air purifiers by CADR numbers?

What the label reveals and hides: Only dust, tobacco smoke and pollen are tested, the largest of all particles.

Performance is certified for only the first 72 hours of operation. Why?

No mention is made of VOCS or any gaseous pollutant.
Example 
of the AHAM CADR rating label
CADR rating tests seek to determine air purifier effectiveness based on performance at removing each of three particle types in indoor air: tobacco smoke, dust, and pollen. The size of these pollutants is quite large in comparison with other particles that may be found in the air. Over 90% of all airborne particles in our homes and offices are smaller and include viruses, bacteria and mold.

CADR air purifier comparisons provide no indication of a filters efficiency at removing these smallest of all particles, the ones that purifiers are generally the least efficient at removing. This test also does not measure gas and odor reduction. Since most people buy air cleaners for these purposes, this standard is of no real value to consumers.

CADR air purifier comparisons are also limited in that they are based on reducing particle levels from sources that emit particles intermittently rather than continually (this is the primary concern about this test not representing real world indoor conditions). If the source is continual, CADR rated air purifiers cannot be expected to be as effective as their rating would indicate.

In addition, CADR air purifier comparisons represent performance that can be expected during the first 72 hours of use. Subsequent performance may fall off greatly, especially in the case of ionic precipitators. Longer-term tests clearly show that collector plate loading by contaminants can reduce efficiency to less than 20%. This can have a severe impact on Clean Air Delivery Rate that would not show up in the CADR testing. Failure to provide consumers with this critical information prevents them from understanding how important it is to follow use and care directions routinely.

The top five reasons the AHAM CADR rating is unreliable

  1. The rating test performed by CADR is not a strict, definitive test. It fails to address the majority of lung damaging airborne particles.
  2. The CADR values reported are based on reducing particle levels from sources that emit particles intermittently rather then continually - this does not emulate a realistic environment. Since sources in normal indoor environments are continual, the devices are not as effective as suggested by AHAM.
  3. The test does not consider the way particles are eliminated. Even ionizers rate well. The well-documented ineffective filtration and dangers of ionizer air purifiers is a good indication that this test should be questioned.
  4. The test does not measure the performance of the elimination of gas and odors, although many people buy air cleaners for this purpose.
  5. The major downfall with the test is that it does not measure long-term performance. The values in CADR air purifier comparisons represent performance that can be expected during the first 72 hours of use. Most air cleaning systems are used for 5,000 hours before filters are replaced. The performance over this span will often be drastically lower and depends to a significant degree on the construction of the air cleaner and the air cleaning technology.
Based on these concerns CADR air purifier comparisons are questionable and fail to really serve the best interests of consumers. The manufacturers of the world’s best air purifiers universally ignore this test. Submitting to it would seem to grant it an air of credibility while failing to really prove the superiority of the air purifiers they have to offer you.

A better standard than the AHAM CADR rating is available

Would you like to know more about the AHAM CADR rating?
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Link to AHAM's official CADR rating site


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An attempt to explain the CADR rating better than the official site

A superior testing method to the AHAM CADR rating went into effect in 2000. It is used to determine HEPA efficiencies in the smallest of particles over extended use. It determines air purifier effectiveness under a worst-case scenario.

It is known as EN1822 (European Norm 1822).

The EN 1822 standard tests air purifier effectiveness over a broad range of particle sizes. This is done to determine the particle size the filter is the worst at removing, known as the Most Penetrating Particle Size (MPPS for short). Then particles of only that size are used to test the filters efficiency at air speeds that reflect actual use conditions.

Since this gives absolute worst-case scenario performance measures, consumers can be assured of real world performance in their own homes.

The first air purifier company to be type tested under this standard was IQAir.

The AirMedic Model by Allerair meets the standards of an EN1822 certified filter capable of removing 99% of particles as small as 0.01 micron, the size range of bacteria and viruses. Find out more about the Allerair Air Medic here.



Your Host J Alan Rodgers

J Alan Rodgers, Home Air Purifier Guide author
Discover how I quit wasting time with good for nothing indoor air purifiers
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