Concerns
about indoor air quality and the rising incidence of asthma and allergies
have made portable air cleaners a big business. US consumers spent
about $275 million on these devices in 2003, and
that number is expected
to increase
to $370 million by 2008.1 But just how effective are these devices?
Are they truly necessary? Can air cleaners remove enough dust, pollen, tobacco
smoke,
pet dander, microbes, and toxic gases, like formaldehyde, to make a difference?
Well, maybe. It depends on how the cleaner is made and maintained. It
also depends on the amount of indoor pollution.
Neither the Environmental Protection Agency (EPA) nor the American Lung Association
recommends depending upon air cleaners as a first-line defense against allergens.
No machine is as effective as source control. That is, no machine will remove
the particles, gases, and odors associated with cigarette smoking as effectively
as having people smoke outside. One of the best ways to reduce house dust mites
is to get rid of carpeting (one of their primary habitats) and using hard surface
flooring instead. Vacuuming with a machine equipped with a HEPA filter every
day or so and regular dusting with a Swiffer duster or electrostatic cloth can
go a long way towards reducing allergy symptoms in those who are sensitive to
dust.
Ventilation is the second tactic to use before turning to air cleaners. EPA has
found that in many cases indoor air is more polluted than outdoor air. Unless
you live in an area with poor air quality, opening windows may be one of the
easiest ways to better indoor air quality. During cold weather, use bathroom
fans to send hairspray and other odors outdoors. In warm weather, air conditioners
can decrease the amount of pollen that enters a home. People with central heating
and air conditioning may find it helpful to use pleated filters, such as 3M Filtrete
Ultra Allergen Reduction and Precisionaire NaturalAire Micro-Particle, instead
of the regular, loose-weave filter. The denser fabric in these pleated filters
capture more particles. They do require the fan to work harder, however, and
may affect energy costs.
Air cleaning devices are considered the third most effective strategy for reducing
indoor pollutants and do not replace the need for the first two. Picking an effective
air cleaner is daunting. Part of the problem is that no industry standard exists.
The Association of Home Appliance Manufacturers (AHAM), Consumers' Union
(Consumer Reports' publisher), and Air-Purifiers-America.com have different
ways of evaluating the devices; and none of these groups test all machines on
the market. AHAM provides voluntary certification of the clean air delivery rate
(CADR) for tobacco smoke, dust, and pollen and the appropriate room size for
each device it tests. CADR is the amount of clean air measured in cubic feet
per minute (cfm) that an air cleaner delivers to a room. Consumers' Union
injects measured amounts of dust and smoke into a sealed test room, then measures
the result after a device has run at high speed for a specified time. The test
is then repeated at low speed. Consumers' Union also includes noise level
in its evaluation. Air Purifiers America tests devices at high speed only in
an office environment with closed doors and windows and with the ventilation
turned off. They believe that this environment is closer to actual conditions
than Consumers' Union's sealed room. Even so, none of these tests
may give a truly accurate picture of a device's long-term performance
in a home with several pollutants.
People have reported symptom improvement when using air cleaners. Few air cleaners,
however, have been tested in placebo-controlled clinical studies that show their
effect on people with asthma and allergies. When sifting through the often-inflated
advertising claims for air cleaners, it is important to keep in mind the EPA's
statement that "no air-cleaning system is available that will effectively
remove all pollutants from indoor air."2
Air Cleaners That Remove Pollen and Other Particles
Air cleaners use mechanical filtration, electronic filtration, gaseous filtration,
UV light, or a combination of these techniques to remove particles and gases
from indoor air. HEPA (High Efficiency Particulate Air) filters are considered
the most efficient mechanical filter for removing particles (pollen, pet
dander, dust, etc.) from the air. Under test conditions, the HEPA material
removes 99.97% of all particles, 0.3 microns or larger. The American Lung
Association says that "particles of 0.3 microns diameter represent
the respirable size most likely to reach and be deposited in the alveoli
of the lungs; they are also the most difficult to remove by mechanical filtration.
Both larger and smaller particles are captured with greater efficiency. So,
for example, HEPA filters with 99.97 efficiency for 0.3 micron size particles
approach 100% efficiency at other particle sizes."3 Pollen, animal
dander, and house dust allergens are larger particles. Particles from cigarette
smoke are more difficult for a mechanical filter to capture.
Air cleaners use fans to pull airborne particles through their systems. Unlike
pollen fragments and animal dander, larger particles, such as house dust and
intact pollen, settle out of the air quickly. They will not enter the air cleaning
device unless they are disturbed and re-suspended in the air. The effectiveness
of HEPA material, employed in an air cleaner, depends upon the amount of air
that flows through the filter, the length of time the filter has been in use,
and the amount of pollution in the air. "The actual efficiency, for
particles of 0.3 microns or larger, of many HEPA-based air purifiers sold today
is below 80%," according to Frank Hammes, President of IQAir, North
America.4
Electronic air cleaners, which include ion generators and electrostatic precipitators,
also remove particles from air. Their effectiveness varies widely. Like mechanical
filters, these systems must have a powerful fan to pull air into the system
in order to be effective. Negative ion generators charge particles as they
pass through the device. These charged particles are attracted to and deposit
on walls, floors, table tops, curtains, furniture, and occupants. Because these
devices do not prevent these charged particles from re-entering the environment,
the particles can still enter a person's lungs. Remember the old trick
of rubbing a balloon on your shirt to build up a static charge, and then marveling
at how the balloon can stick to the wall? Ion generators work on the same principle.
Eventually, that balloon loses its charge, falls, and bounces around the room.
Similarly, charged particles will return to the air unless the room is cleaned.
Negative ion generators are rarely effective by themselves.
Electrostatic precipitators also charge particles; but, unlike ion generators,
they have metal plates or other medium with the opposite charge that collects
the charged particles, preventing them from returning to the environment. Their
ability to remove particles from the environment depends upon the air flow
rate generated by a fan, the strength of the electrical field, and the area
size of the collecting plates. The greater the area, the more particles the
device can capture. These plates must be cleaned frequently so that more charged
particles can be caught. Otherwise, the charged particles simply re-enter the
air. Tabletop devices are less effective than console devices simply because
they do not have as powerful a fan or as big a collection area.
In general, electronic air cleaners that lack a fan and a mechanical filter
or other particle collection device are very ineffective. A study by D.W. Hacker
and E.M. Sparrow (Indoor Air 2005;15:42-431) compared six randomly chosen,
commercially available air cleaners. Three used HEPA filters, and three used
ion generators or electrostatic precipitation. The authors did not name the
six cleaners, but they did provide pictures. Each device was tested in different
locations in a bedroom setting, under different ventilation conditions, and
using two different fan speeds. The electronic cleaner that lacked a fan had
no effect on particle pollutants. The other two electronic air cleaners did
have fans. The one that performed best of the three contained several electrostatically
charged plates to collect particles. That device performed as well as and,
in some conditions, better than some of the HEPA cleaners. Unlike HEPA air
cleaners, however, many electronic air cleaners produce health-compromising
ozone.
Ozone Problems
Ion generators, electrostatic precipitators, and air cleaners that use UV light
produce varying amounts of ozone. Ozone is a highly reactive molecule composed
of three atoms of oxygen. Breathing ozone damages the lungs, which is why
it is one of the pollutants monitored by EPA's air quality index. "Relatively
low amounts can cause chest pain, coughing, shortness of breath, and throat
irritation."5 Ozone decreases lung function, worsens asthma, and brings
a higher risk of respiratory infection.
Ozone generators are being promoted as air cleaning devices. Their popularity
encouraged the EPA to produce a publication about the subject: "Ozone
Generators that are Sold as Air Cleaners: an Assessment of Effectiveness and
Health Consequences." This document cuts through the hype. Ozone does
not remove particles from the air. Ozone can remove some odors but only at
concentrations that exceed public health standards. While ozone safely inhibits
microbial growth in water, it does the same in air only when ozone concentration
is five to ten times public health standards. Ignore the spin that promises "energized
oxygen" and "pure air" and avoid ozone generators altogether.
The amount of incidental ozone produced by electronic air cleaners varies.
Some devices, such as the highly rated BlueAir cleaners, meet FDA safety guidelines
for medical devices, which require that ozone output be no more than 0.05 ppm.
Even small amounts of ozone can cause headaches or irritate the respiratory
tract if a person is ozone-sensitive. The Friedrich C-90B air cleaner, for
example, received a high rating in Consumer Reports. This electrostatic precipitator
has a pre-filter to capture large particles (i.e., hair, lint), an ionizing
section, collector plates, and a carbon filter to adsorb some gases. Although
this air cleaner effectively removes particles, Air Purifiers America did not
rate it as high because of complaints about headaches and the "musty" smell,
attributed to ozone.
A couple of very popular air purifiers — Sharper Image's Ionic Breeze
and Oreck XL — not only produce potentially unsafe levels of ozone, they
also "fail to significantly clean the air," according to Consumer
Reports. Over two million of Sharper Image's Ionic Breeze have sold,
thanks to a flood of advertising and its purported ease of operation and maintenance.
Consumer Reports has produced several articles that challenge the effectiveness
and safety of Sharper Image's Ionic Breeze and Oreck's XL. Both
are negative ion generators. Ionic Breeze does not have a fan, which is why
it runs so quietly. Oreck XL is a small, tabletop unit with very low air exchange.
Its collector plates provide too little area to effectively capture particles.
Its "charcoal absorbers" contain scent cartridges to mask odors.
Because of Consumers' Union's negative articles, Sharper Image
filed a libel suit against the organization. The suit was dismissed in 2005,
and the judge ordered Sharper Image to pay Consumers' Union $525,000
for its legal costs.
Air Cleaners for Gases, Smoke, and Microbes
While HEPA filters and electronic precipitators can effectively collect particle
pollutants, neither collects gaseous pollution. Many high-priced air cleaners
include activated carbon filters, weighing several pounds, to capture a variety
of gases. (Pads with a few ounces of carbon are ineffective.) Activated carbon
does not adsorb all gases, however. Formaldehyde, commonly off-gassed by foam
insulation and other building materials, and some other gas pollutants can
only be captured by chemisorbents. Chemisorbents contain potassium permanganate,
copper oxide, or other chemically active materials that attract and combine
with specific gases. As with all air cleaners, air flow rate and the amount
of pollutant held in the filter affects the air cleaner's actual efficiency.
UV light is also included in some air cleaners. UV light is said to kill microbes
in the air. While UV light is recognized for its germicidal properties, I was
not able to find studies that verified UV light's ability to kill germs
during the seconds that air flows through a device. Manufacturers should be
able to show you some evidence that UV treatment as used in their device actually
does some good. Air cleaners that include UV lights tend to be more expensive.
Choosing an Air Cleaner
The first step in choosing an air cleaner is to decide what you want it to
do. If pollen and pet dander are the main culprits, well-made devices using
a HEPA filter and/or electrostatic precipitator will be effective. If cigarette
smoke is the problem, a HEPA filter or effective electrostatic precipitator
to remove particles and a good activated carbon filter to remove gaseous
pollution would be the best bet. (Removing the source by smoking outside
is even more effective.) Beware of "air cleaners" that merely
mask the smell by adding a chemical scent.
Air flow rate is the second factor to consider. Check the clean air delivery
rate (CADR) for the models that interest you. The cubic feet per minute rate,
calculated at the machine's high speed, will give a good idea of its
effectiveness in giving at least six air changes per hour for a given room
size. Allergy Buyers Club reminds consumers that "a room air cleaner
is most effective located in a single room, it will not be so effective if
you expect it to clean multiple rooms simultaneously."6 Console units
are more effective than tabletop units. The smaller devices have small filters
that fill up quickly and have less effective fans, resulting in poor air circulation.
Filter replacement is another consideration. How much do the filters cost?
How often does the manufacturer say filters need to be replaced? Be aware that
the actual lifespan of any air cleaner depends upon the amount of pollution
in the room. Some air cleaners have a change filter light that correlates to
the hours that the device has been running. Allergy Buyers Club says, "No
machine is currently measuring the amount of pollutants absorbed by the filter.
Naturally, your filters will last longer in a nice clean suburb as opposed
to one located in the center of New York City."7 Ideally, the air cleaner
should have an inexpensive pre-filter to prevent hair, lint, and other large
particles from clogging more expensive HEPA filters or activated carbon filters.
By changing pre-filters every few months, a HEPA-filter can remain effective
for as long as three years. Some air cleaners include the pre-filter, HEPA,
and activated carbon filters in one unit that can be easily replaced. The drawback
is that the various sections may clog at different rates, affecting the efficiency
of the others. Devices that use only electrostatic precipitators have the advantage
of having no filters to replace. In order to maintain effectiveness, however,
the collector plates need to be cleaned frequently according to manufacturer's
instructions.
Noise is another factor. The fans, running at high speeds, can be louder than
a coffee grinder — a real drawback if you are trying to sleep or are sensitive
to sound. Some air cleaners include the noise levels created at each fan speed
in their specifications. The League for Hard of Hearing says that 40 decibels
is the noise level of a quiet library, 50 decibels is the level of a refrigerator,
and 70 decibels is a coffee grinder.
And then, there's the initial cost and the machine's warranty.
Most of the top-rated air cleaners sold on the Internet cost $500 to $700 or
more. Many retail sites let buyers return the device for any reason within
30 days. The buyer usually pays return shipping and, often, a 15% re-stocking
fee. If you are returning a $700 machine, you may be paying over $105 to find
out that the machine doesn't work for you.
My Personal Picks
If I were looking for an air cleaner to reduce pollen and animal dander in
a room, I'd probably try Whirlpool's Whispure 45030, which
costs about $250 and can be bought at a local Lowe's or Sears (www.whispure.com has
a store locator). The Whispure has a charcoal pre-filter and a true HEPA
filter. This air cleaner has qualified for the government's Energy
Star program, which indicates that it uses less energy than some other cleaners.
It also runs quietly according to Consumers' Union.
If I were trying to reduce particle exposure while sleeping, I'd check
out the PureNight Sleep Air Purifier, which costs around $500. This HEPA filter
device attaches to the headboard of the bed and uses laminar airflow to send
filtered air over the sleeper and toward the foot of the bed without turbulence.
The Pure-Night device was evaluated as being highly effective in Hacker and
Sparrow's Indoor Air study, which compared six different air cleaners.
IQAir Health-Pro Plus may be helpful for people with serious allergies who
want to remove gases as well as particles. The HealthPro Plus contains a pre-filter,
HEPA filter, and an eight-pound, activated carbon filter with activated alumina
and potassium permanganate. The cost for this IQAir unit runs about $800. Previous
experience with an ion generator has made me wary of any device that may produce
ozone.
Final Words
Allergy Buyers Club, Air Purifiers America, and Consumer Search each have reviews
of several air cleaners and recommendations (See
Sidebar). But these sites
are not exhaustive and may not even sell all the best devices. Just remember
that a good air cleaner may help indoor air quality, but it will not take
the place of pollutant source removal, good ventilation, and regular house-cleaning.
And if you do buy an air cleaner, start using it right away, before any return
policy runs out. See if it works for you. That's the final test — if
it actually relieves your allergy symptoms.
Jule
Klotter
Contributing Editor
Jule11k@yahoo.com
Notes
1. Global Information, Inc. US Consumer Water & Air Purification
Systems to Reach $1.6 Billion in 2008. Available at www.the-infoshop.com/press/fd23272_en.shtml.
Accessed on March 21, 2006.
2. US Environmental Protection Agency. Residential Air Cleaning Devices:
A Summary of Available Information. Washington, DC: Office of Air and
Radiation (OAR), Indoor Environments Division (IED); February 1990.
EPA 400/1-90-002. Available at http://www.epa.gov/iaq/pubs/residair.html.
Accessed on March 14, 2006.
3. American Lung Association. Search LungUSA — Types, Effectiveness,
and Health Impact. Available at www.lungusa.org/site/apps/s/content.asp?c=dvLUK9O0E&b=
34706&ct=67133. Accessed March 14, 2006.
4. Hammes F. The seven sins of air filter manufacturers. Available
at www.allergybuyersclub.com/acr/acr_14.shtml?psysVid=07fx31os. Accessed
on March 15, 2006.
5. U.S. Environmental Protection Agency. Ozone generators that are
sold as air cleaners: an assessment of effectiveness and health consequences.
Available at http://www.epa.gov/iaq/pubs/ozonegen.html. Accessed March
14, 2006.
6. Interview with NBCI on Air Cleaners. Available at www.allergybuyersclub.com/acr/acr_21.shtml?psysVid=07fx31os.
Accessed on March 15, 2006.
7. Interview with NBCI on Air Cleaners. Available at www.allergybuyersclub.com/acr/acr_21.shtml?
psysVid=07fx31os. Accessed on March 15, 2006.
References
Air Purifiers America. Editor reviews and recommendations. Available
at www.air-purifiers-america.com/ed_reviews.asp. Accessed on March
15, 2006.
Air Quality Scientists. Air cleaners: the pros and cons of their use
in your home and office. Available at www.aerias.org/kview.asp?DocID=135&spaceid=1&subid=8.
Accessed on March 15, 2006. (4/13/06: Full
link no longer works.)
Allergy Buyers Club. Air Purifiers, air cleaners — comparisons,
ratings, reviews. Available at www.allergybuyersclub.com/compare-air.html?psysVid=07fx31os.
Accessed on March 15, 2006.
American Lung Association. Search LungUSA — Types, Effectiveness
and Health Impact. Available at www.lungusa.org/site/apps/s/content.asp?c=
dvLUK9O0E&b=34706&ct=67133. Accessed March 14, 2006.
Association of Home Appliance Manufacturers. 2005 Directory of Certified
Room Air Cleaners. October 2005. Available at www.cadr.org/consumer/index.html.
Accessed on March 14, 2006.
ConsumerReports.org. New concerns about ionizing air cleaners. May
2005. Available at www.consumerreports.org/cro/appliances/ionizing-air-cleaners-505/overview.htm.
Accessed on March 14, 2006.
ConsumerReports.org. Air cleaners: The truth behind the accolades.
Available at www.consumerreports.org/cro/appliances/ionizing-air-cleaners-505/air-cleaners-the-truth-behind-the-accolades.htm.
Accessed on March 14, 2006.
ConsumerSearch.com. Air Purifiers, Air Cleaners, Home Air Purifiers,
Ionizers. Updated March 2006. Available at www.consumersearch.com/www/house_and_home/air-purifiers/fullstory.html.
Accessed March 14, 2006.
ENERGY STAR Room Air Cleaners. Available at www.energystar.gov/index.cfm?c=room_
airclean.room_airclean. Accessed March 21, 2006.
Global Information, Inc. US consumer water & air purification systems
to reach $1.6 billion in 2008. Available at www.the-infoshop.com/press/fd23272_en.shtml.
Accessed on March 21, 2006.
Hacker DW, Sparrow EM. Use of air-cleaning devices to create airborne
particle-free spaces intended to alleviate allergic rhinitis and asthma
during sleep. Indoor Air. 2005; 15:
420-431. Available at www.purenight.com/university_test_results/.
Accessed March 15, 2006.
Hammes F. FAQ on filtration of gaseous pollutants and odors. Available
at www.allergybuyersclub.com/acr/acr_15.shtml?psysVid=07fx31os. Accessed
on March 15, 2006.
Hammes F. The seven sins of air filter manufacturers. Available at
www.allergybuyersclub.com/acr/acr_14.shtml?psysVid=07fx31os. Accessed
on March 15, 2006.
Interview with NBCI on Air Cleaners. Available at www.allergybuyersclub.com/acr/acr_21.shtml?
psysVid=07fx31os. Accessed on March 15, 2006.
MSNBC.com. Consumer Reports calls air purifer "unhealthy." April
5, 2005. Available at www.msnbc.msn.com/id/7391185/. Accessed on March
15, 2006.
US Environmental Protection Agency. Ozone generators that are sold
as air cleaners: an assessment of effectiveness and health consequences.
Available at http://www.epa.gov/iaq/pubs/ozonegen.html. Accessed March 14,
2006.
US Environmental Protection Agency. Residential
Air Cleaning Devices: A Summary of Available Information. Washington, DC: Office of Air and
Radiation (OAR), Indoor Environments Division (IED); February 1990.
EPA 400/1-90-002. Available at http://www.epa.gov/iaq/pubs/residair.html.
Accessed on March 14, 2006.
General Information
Resources
Air Quality Scientists provides information about indoor air quality
at www.aerias.org
Association of Home Appliance Manufacturers publishes a directory
of certified room air cleaners. The voluntary program verifies clean
air
delivery rates with independent testing.
www.cadr.org/consumer/index.html
Consumer Search has an informative article on portable air cleaners
at its web site. It also critiques organizations and web sites that
review the devices and offers its own "Best Picks."
www.consumersearch.com (Click "air purifiers" under "House & Home.")
Consumers Union publishes Consumer Reports. Some of its informative
articles are available online, but its complete reviews require a
subscription. Consumer Reports (October 2005) contains its most recent
reviews of
portable air cleaners. (Check your local library.) www.consumerreports.org (Air cleaners are under "appliances.")
Energy Star room air cleaners are 35% more energy-efficient than
standard models.
www.energystar.gov (Click "Products." Room Air Cleaners
are under "Appliances.")
US Environmental Protection Agency has several pamphlets on indoor
air quality, residential air cleaning devices, and ozone generators.
www.epa.gov (Put "air
cleaners" in the search.)
Reviewers Who Sell Air Cleaners
Air Purifiers America tests and reviews the models that it sells.
www.air-purifiers-america.com; 1-800-334-1494 (8 AM - 5 PM, CT, M-F)
Allergy Buyers Club has several informative articles about air cleaners.
www.allergybuyersclub.com; 1-888-236-7231 (8 AM - 11 PM, EST, everyday)
Partial List of Effective Air Cleaners
BLUE AIR 501 contains an ionizer, HEPA filter, and activated carbon
filter. Energy Star approval (energy efficient). FDA Medical Device
(meets FDA ozone limits). Ten year limited warranty. Cost $534. www.blueair.com;
1-888-258-3247
FRIEDRICH C-90A has a pre-filter, ionizing section, collector plates,
and carbon filter. One year limited warranty. Cost $499. www.friedrich.com/aircleaner/;
1-210-357-4400
IQ HEALTHPRO PLUS has a pre-filter, HEPA filter, and 8 lb. activated
carbon filter with activated alumina with potassium permanganate. Five
year limited warranty. Cost $835. www.iqair.us; 1-877-715-4247
NQ CLARIFIER contains a pre- and post-filter, HEPA filter, 2/4 UV lamps,
and a 15 lb. activated carbon filter. Two year limited warranty. Cost
$699-$1099. www.clarifierpurifiers.com; 1-877-633-9464 (9 AM - 7 PM,
EST, M-F)
PURENIGHT SLEEP AIR PURIFIER attaches to the headboard of a bed. It
has a pre-filter and HEPA filter. Five year limited warranty. Cost
$499. www.purenight.com; 1-800-248-9500
WHIRLPOOL 45030 has a charcoal pre-filter and HEPA filter. Energy Star
approval (energy efficient). One year limited warranty. Cost $259.
www.whispure.com; 1-866-698-2538 (8 AM - 6 PM, EST, M-F)
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