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Is the AHAM CADR rating reliable when choosing an 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. |
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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
- The rating test performed by CADR is not a strict, definitive
test. It fails to address the majority of lung damaging airborne
particles.
- 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.
- 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.
- The
test does not measure the performance of the elimination of gas and
odors, although many people buy air cleaners for this purpose.
- 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
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.
Return to top of article.Return to Home Air Purifier Guide home page.
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