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)