Ozone Generators Create Home Smog

Air Purifiers That Produce Ozone May Be Hurting Your Health

Medically Reviewed by Louise Chang, MD on May 11, 2006
From the WebMD Archives

May 11, 2006 -- You can create dangerous smog levels in your own home withan ozone-generating air purifier.

The finding comes from a study of ozone-emitting air purifiers by Sergey A.Nizkorodov, PhD, and colleagues at the University of California, Irvine. Theresearchers studied 13 air purifiers known to give off small and large amountsof ozone, a major ingredient in air pollution.

Included in the study were several ionic air purifiers made by The SharperImage, including the popular Ionic Breeze Quadra. These machines producedetectable levels of ozone. But they did not emit dangerous levels of ozone,except when a Quadra model intended for a large room was tested in a tinybathroom.

Ozone generators, however, were a different story. As they are designed todo, they put a lot of ozone into indoor spaces. The devices quickly causedozone buildups to levels that would trigger severe smog alerts for outdoorair.

"If I put one in my office, I can generate a stage 2 ozone level if Iwant to," Nizkorodov tells WebMD. "This is the problem -- right now itis not controlled. Air purifiers that make ozone above a certain rate should bebanned. The public should not be allowed to buy them."

Ozone is great in the upper atmosphere, where it protects the Earth fromharmful radiation. Ground-level ozone, however, isn't our friend. According tothe American Lung Association, ozone exposure may lead to premature death,shortness of breath, chest pain when inhaling deeply, and wheezing andcoughing. High ozone levels irritate the lung and make asthma worse.

The Nizkorodov study, funded by the National Science Foundation, appears inthe May issue of the Journal of the Air & Waste ManagementAssociation.

Ozone Generators vs. Ionic Air Purifiers

It's easy for consumers to be confused. Three basic kinds of devices callthemselves air purifiers. None is foolproof. Consumer Reports has found that"even the best air cleaners could be a frivolous investment."

There's no ozone emission from air purifiers that use only high-efficiencyparticulate air filters (HEPA filters) to cleanse the air. Ionizing airpurifiers, because of their electric charge, do create ozone. Consumer Reports has warned thatthey may give off potentially harmful ozone levels.

"There are plenty of ionic air purifiers; only a small fraction makeozone," Nizkorodov says.

Mark Connelly, senior director of appliances and home improvement forConsumer Reports, oversees the magazine's air-cleaner tests.

"You don't want to say that anything that generates ozone is bad,"Connelly tells WebMD. "A printer produces ozone, but just because printerssit on people's desks doesn't mean they should be taken off the market. But thepeople who buy air purifiers are most susceptible to the problems they create.You buy it to make things better, and it ends up making things worse foryou."

Whatever ozone comes from ionic air purifiers pales in comparison to theamount produced by ozone-generating air purifiers. These machines make ozonefor one reason: That's what they are designed to do.

"Ozone is a very effective way of disinfecting water -- and some believeit is also possible to do this in the air," Nizkorodov says."Unfortunately, at the concentrations you need to destroy germs andpollutants, the ozone levels are so high you cannot safely use it."

In a small bathroom, the UCI researchers found that one ozone generator, theEZ-COM Air Purifier, took only a half hour to build up ozone to a smog levelthat would force school closings if detected in a city's air. In a1,250-square-foot office, the device took about a half hour to build ozone tosmog levels that would trigger unsafe air alerts.

By contrast, the Sharper Image Ionic Breeze Quadra model -- an ionic airpurifier, not an ozone generator -- built ozone to a maximum level of 40 partsper billion (ppb) in a large office. The FDA considers medical devices safe ifthey emit less than 50 ppb of ozone. The World Health Organization considerseight-hour ozone levels of 60 ppb to be acceptable.

The Quadra did make the air unsafe when used in a small bathroom -- not theproducts' intended use, says Sharper Image spokeswoman Suzie Stephens.

"Sharper Image products were included in the study and, in fact, met allsafety standards for ultra-low trace ozone emissions when the appropriate-sizedmodels were used in the manufacturer-recommended room sizes," Stephenstells WebMD. "Why they chose to place the unit in a room size for which itis clearly not intended nor used is inexplicable."

Stephens worries that the UCI study sows confusion by testing ionic airpurifiers alongside ozone generators. Indeed, she points to news reports on thestudy that confused Sharper Image products with ozone generators.

"The study found that ozone generators, not ionic air purifiers whenused appropriately, can generate potentially unsafe levels of ozoneindoors," Stephens says. "None of the Sharper Image air purifiers areozone generators."

Government Action on the Way?

While Consumer Reports has been critical of ionic air purifiers --including explicit criticism of the Sharper Image Ionic Breeze Professionalwith OzoneGuard -- it is far less worried about these devices than about ozonegenerators.

"We slammed ozone generators back in 1992 -- but they are still beingmarketed to unsuspecting people," he says. "Those people mostsusceptible to harm are cranking ozone into their lungs. Ozone generatorsshould be regulated first and foremost."

There's already a bill before the California legislature to regulate thesedevices. And the California Air Resources Board will meet on May 25 to updateits recommendation on ozone generators.

Nizkorodov says he thinks California will set a limit on how much ozone adevice will be allowed to generate. He guesses the limit will be between 10 and100 milligrams of ozone per hour -- and his bet is on the lower limit.

His study found that the Sharper Image Ionic Breeze Quadra puts out 2.2milligrams of ozone per hour -- far below the lowest limit California is likelyto set.

On the other hand, ozone generators fail the test. The EZ-COM Air Purifierput out 68 mg/hour, while the Air-Zone XT-400 put out a whopping 220mg/hour.

Show Sources

SOURCES: Britigan, N. Journal of the Air & Waste Management Association, May 2006; vol 56, prepublication copy. Consumer Reports web site. ConsumerSearch web site. U.S. Environmental Protection Agency, "Ozone Generators that are Sold as Air Cleaners: An Assessment of Effectiveness and Health Consequences," accessed May 11, 2006. American Lung Association, "Residential Air Cleaning Devices: Types, Effectiveness and Health Impact," accessed May 11, 2006. Sharper Image web site. Sergey Nizkorodov, PhD, assistant professor of chemistry, University of California, Irvine. Suzie Stephens, public relations and marketing manager, The Sharper Image, San Francisco. Mark Connelly, senior director of appliances and home improvement, Consumer Reports.

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