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HealthPro
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The Seven Sins of Air Filter Manufacturers
by Frank Hames, President - IQAir, North America |
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With estimated sales of over 4 million units in 1999 in the
United States, room air purifiers have become standard
appliances in many households and offices. Manufacturers of room
air purifiers must strive - harder than anyone else in the air
purification industry - to provide low cost products to their
consumers. This has resulted in air cleaners with HEPA
technology selling for as little as $80.00. While making air
cleaning technology affordable is a commendable goal; misleading
marketing statements and questionable air cleaning performance
have many users disappointed.
This article attempts to draw attention to a number of deceptive
marketing practices, that air purifier manufacturers use, which
are detrimental to the credibility of the air cleaning industry
as a whole.
Since the science of air cleaning is a complex one, finding
one's way through the maze of unsubstantiated claims and
misinformation is a difficult task even for the most alert and
critical consumer. Seven common industry practices in particular
continue to confuse consumers and air cleaning professionals. |
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1. Theoretical HEPA Efficiency vs. Actual System Efficiency |
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Due to the high efficiency, reliability and proven track-record,
HEPA technology has become the industry standard for particulate
filtration in critical environments, such as semi-conductor
clean rooms and hospital operating rooms.
Recognizing the great marketing potential of the term
"HEPA", many manufacturers are using it to project a
high- performance image onto their room air purifiers. What most
HEPA-based air purifiers manufacturers conveniently omit to tell
the consumer, is that their air purifiers provide nowhere near
the performance level of professional HEPA filter systems used
in hospitals and clean rooms.
Often consumers are misled about an air purifier's efficiency in
removing pollutants. Statements like "effectively removes
99% of all airborne allergens" or "efficiently scrubs
the room free of air pollutants", lead consumers to believe
that these air purifiers remove virtually all of the impurities
from the air in a normal indoor environment.
Claims about HEPA-based air purifiers often state 99.97%
filtration efficiency. In most cases, this is also not true. The
actual efficiency, for particles of 0.3 microns or larger, of
many HEPA-based air purifiers sold today is below 80%. The
"99.97%" refers to, in most cases, the theoretical
efficiency rating of the filter paper that is used in the air
cleaning device at 0.3 microns or larger. The performance gap
between HEPA-based room air purifiers and professional HEPA
filter systems is mainly due to cutting corners in
mass-production and profit maximization. There are a number of
reasons why most HEPA-based room air purifiers do not achieve
actual HEPA performance: |
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1. |
HEPA-rated filter media is not used. |
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2. |
The HEPA filter media gets damaged during the pleating process
(HEPA media breaks easily).
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3. |
There is leakage between the pleated HEPA filter pack and the
filter frame.
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4. |
There is leakage between the HEPA filter frame and the air purifier
housing. |
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Only
very few manufacturers state the actual overall efficiency of
their device, and even fewer guarantee and certify their air
purifiers. |
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2. Overstating Actual Air Delivery Rates |
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Even the most efficient room air purifier in the world would not
impact a room's air quality level, if it were not able to pass
enough air through its filters. The amount of air that an air
purifier is able to process (air flow rate) is usually expressed
in cubic feet per minute (cfm). Consumers are often misled by
exaggerated or false claims by manufacturers regarding air flow
rates.
One common trade practice is to state the free-flow air handling
capacity of the fan motor (i.e. without filters installed),
rather than the actual air flow rate (i.e. with all filters
installed).
Many manufacturers don't even make this vital air purifier
statistic available to consumers. Instead, many state a suitable
room size, without mentioning how many air changes per hour the
air purifier would manage to produce in that size room.
Only very few manufacturers state the actual airflow rate of
their device (with all filters installed), and even fewer
guarantee and certify their air purifier's air flow rate. |
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3. ULPA is NOT Better than HEPA |
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In an
effort to differentiate air purifiers from the mass of HEPA air purifiers on the market, some manufacturers have
introduced air purifiers, which supposedly use ULPA technology.
ULPA stands for Ultra Low Penetration Air and is used in modern
clean rooms. The difference between HEPA and ULPA is the
efficiency rating of the filter media. Typical HEPA filter media
has an efficiency of 99.97% at 0.3 microns, whereas ULPA media
has an efficiency rating in excess of 99.999% at 0.12 microns.
Stressing the higher efficiency at smaller particle size,
manufacturers of ULPA-based air purifiers claim that these
devices are superior to HEPA-based air purifiers. Unfortunately,
this is a perfect example where the search for a better sales
pitch has resulted in an inferior product, since the reverse
tends to be the case. All things being equal, an air purifier
that uses ULPA filter media will be less effective in reducing
the particle concentration in a typical room, than the same air
purifier equipped with HEPA filter media. And as with many
HEPA-based air purifiers, many ULPA-based air purifiers come
nowhere close to actually delivering 99.999% particle-free air.
While ULPA filter media has the potential to remove more
particles than HEPA filter media, that advantage is lost in room
air purifiers, due to the reduction of air flow caused by the
denser ULPA filter media. ULPA filter media typically allow
20-50% less air to pass than HEPA filter media, resulting in
fewer air changes per hour in a given room. |
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4. Ineffective Gas Phase Filtration |
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In
many cases room air purifiers are purchased to deal with gaseous
contaminants and odors. So it comes as no surprise that most
manufacturers claim to use some technology to reduce gases and
odors. The most common technology adopted by air purifier
manufacturers for the removal of gaseous pollutants is activated
carbon. While activated carbon in its granular form is
unquestionably effective for the removal of many gaseous
contaminants, most room air purifiers on the market today use
carbon fiber pads, which are only impregnated with activated
carbon dust. These filter pads contain only a few ounces of
actual activated carbon and as a result, are essentially
ineffective for the removal of gases and odors.
Some manufacturers claim that their activated
carbon filter eliminates all gaseous pollutants and odors, a
feat that is scientifically impossible. Specific gaseous
contaminants need specific gas phase filtration technology.
Activated carbon does not efficiently adsorb low molecular
weight gases. For this reason, special sorbents are needed to
effectively deal with pollutants, such as formaldehyde, hydrogen
sulfide and ammonia.
Many room air purifiers that use granular activated carbon also
use Zeolite. Zeolite is a natural mineral, whose pore structure
is supposed to be better suited for the removal for gaseous
compounds like formaldehyde and ammonia. In fact, there is no
reliable scientific evidence to show that zeolite is able to
remove any gaseous compound better than specialty impregnated
carbons or impregnated alumina. So why is Zeolite used? Zeolite
is an inexpensive "filler" that is less expensive than
activated carbon. Secondly, the concept of using two different
substances to control gases and odors sounds quite promising to
the unsuspecting customer. |
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5. Sacrificing Long-Term Performance |
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While most tests and evaluations of air purifiers assess only
air purifier performance during its first few hours of usage,
the real test for air cleaning effectiveness is long term
performance. Unfortunately, most manufacturers cut costs on
features that would enhance long-term performance.
One standard industry practice is the use of ineffective pre-
filtration. In HEPA based air purifiers, it causes the HEPA
filter to become clogged at a rapid rate. This in turn reduces
the air flow rate, thus resulting in fewer air changes per hour
in a given room. This is a particularly serious issue, since
some manufacturers inform their consumers that their HEPA
filters will only need replacing every 3 to 5 years.
Insufficient pre-filtration, also, causes air purifiers with
substantial granular activated carbon filters to quickly lose
their gas phase adsorption potential. Dust particles - that
should be trapped by pre-filtration - clog the miniscule pores
of the activated carbon, and destroy its holding capacity to
adsorb gases. Another reason for poor long term performance of
air purifiers is that some air cleaning technologies suffer
drastic reductions in air cleaning efficiency without regular
maintenance or frequent filter change.
Air purifiers with electrostatic precipitator technology
experience drastic efficiency reductions as the collector plates
become covered with particles. Air purifiers that use
electrostatically charged fibers (electrete) also rapidly loose
filter efficiency with particulate loading, especially in the
presence of tobacco smoke. |
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6. Frequent and Expensive Filter Replacement |
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While the initial purchase cost for many room air purifiers is
relatively low, the cost of replacement filters can be
substantial. Here are some reasons why many air cleaners require
frequent and expensive filter replacement:
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Lack
of effective pre-filters that protect activated carbon and HEPA
filters from premature clogging.
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Use
of small filter cartridges with low holding capacity for
pollutants.
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Filter
replacement instructions that base filter replacement intervals
on time passed (e.g. every 6 months) rather than actual usage
and degree of air pollution.
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Combining
several different filter stages in one filter cartridge, thus
forcing the user to replace all filters at once, even if only
one filter stage is used up.
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7. Trying to be All Things to All People |
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While many air purifier manufacturers offer several models,
these models often vary only in size, rather than air cleaning
technology. And since manufacturers like to have their product
appeal to as many potential customers as possible, they sell one
and the same unit as the ideal solution for pet allergens,
pollen, mold spores, microorganisms, tobacco smoke, odors,
traffic fumes and chemicals, etc. In fact, some manufacturers
claim that by virtue of using a multitude of filter stages their
air purifier is more effective. Unfortunately, the effectiveness
of the air purifier suffers, because more filter stages mean
higher air resistance and lower air delivery. Air purifiers that
only contain filter stages matched to the user's requirements,
offer superior filtration efficiency and air flow.
Conclusion Industry organizations, like AHAM, have set out to
establish some reference point for air purifier performance,
they have not succeeded to make comparison shopping for air
purifiers a simple task. AHAM's testing protocols do not
evaluate actual particle retention, gas phase filtration or
long-term performance of air purifiers.
So what are the lessons when evaluating air purifiers? Don't
believe every claim made by manufacturers. Realize that a $80
air purifier will have serious limitations. Ask manufacturers to
substantiate their claims with independent evidence. Check the
underlying technology and investigate whether it has been
properly implemented. Use tools that allow objective evaluation
of air cleaning performance, such as laser particle counters, to
check manufacturer's particulate efficiency claims and evaluate
actual particle reduction.
Misleading claims regarding air purifiers and air filters have
in the past led to decisions and orders of the Federal Trade
Commission against manufacturers, and are likely to do so in the
future unless manufacturers practice better self-restraint and
self-regulation. Participating in sound business practices and
making scientifically proven claims will restore lost faith in
room air purifiers, allowing consumers to make informed purchase
decisions - based not only on price but, also, on actual
performance.
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