In its latest review of air purifiers, Consumer Reports (CR) has again recommended against the Ionic Breeze Quadra, despite the addition of a device meant to eliminate some of the ozone emitted by the product. Its manufacturer, Sharper Image, disputes the assessment, saying the magazine's evaluation method is flawed.

The exchange extends a feud between CR and Sharper Image that started two years ago, after the magazine gave a failing grade to an earlier version of the air cleaner. Sharper Image sued Consumers Union, which publishes CR, for libel in 2003 after earlier reports said that the Ionic Breeze performed poorly at removing dust and smoke particles from the air. A federal court dismissed the suit.

CR's October 2005 issue -- which gives the Ionic Breeze "poor" grades for its ability to clean dust and smoke particles from the air -- went to press before the release of the newest Ionic Breeze model, which includes OzoneGuard, a feature that partially clears ozone from the air. CR then published a supplemental report online that gave the OzoneGuard model poor marks.

"Our air-cleaning tests show that the Ionic Breeze with OzoneGuard does a poor job of removing smoke, dust and pollen particles from the air when new and after 500 hours of continuous use," reported the CR update. "While earlier versions of the Ionic Breeze significantly exceeded the ozone limit in the voluntary, industry-standard Underwriters Laboratory test, the Ionic Breeze with OzoneGuard still adds ozone to the air, measuring just within the test limit" of 50 parts per billion (ppb).

The Ionic Breeze is an ionizing air cleaner, which electrically charges airborne particles and traps them on oppositely charged metal plates. Ozone is a byproduct of this process that can in large enough quantities aggravate asthma, damage the lungs and irritate the respiratory system, according to the Environmental Protection Agency. Sharper Image leads the ionizer market; ionizers, overall, make up about a quarter of the $410 million-a-year air cleaner market, according to a CR report on air cleaners released in May.

High-efficiency particulate air (HEPA) filter cleaners -- which trap most particles and remove odors while producing much lower amounts of ozone -- make up another category of air purifiers. Use of a third type, called ozone generators, is discouraged by many experts because of the emission of high amounts of ozone.

Sharper Image took issue with the testing methods used by CR.

CR based its findings on the Clean Air Delivery Rate (CADR) system, the industry standard for evaluating air cleaners. CADR measures the rate at which contaminants are removed from the air, according to Richard Shaughnessy, an American Lung Association adviser and program director of indoor air research at the University of Tulsa.

"We consider any air cleaner with a clean air delivery rate (CADR) of under 100 to be ineffective," CR reported in its update. "CADR values for the Ionic Breeze were consistently in the 20s for dust and smoke and in the 30s for pollen. . . . Our highest-rated air cleaner removed particles from the air roughly 20 times faster than the Ionic Breeze."

Sharper Image says the CADR standard is meant to evaluate HEPA cleaners and should not be the sole way to judge its product. "It's a rate measurement," said Michelle Arney, the company's vice president of intellectual property and legal affairs. "It's not a measurement of ultimate cleanliness."

"CADR is not designed to test the new Ionic Breeze technology, which has a low air-speed flow versus conventional kinds of air cleaners that rely on a high-speed airflow for their operation," Sharper Image's Web site reports. "One key to the Ionic Breeze's efficiency and effectiveness is its silent, 24-hour operation. Its airflow is slower but constant."

But experts at CR and elsewhere say CADR has long been used to evaluate a variety of devices. They say it's an effective way to test all types of air cleaners.

"Any manufacturer that says CADR is not indicative or not representative for their product -- that's absurd," said Shaughnessy, who said he has no ties to any air cleaner manufacturers. CADR is "the best thing we have . . . right now for what is a comparative analysis of how these air cleaners" stack up against each other, he said.

The addition of OzoneGuard came just months after CR issued a critical report in May that focused heavily on the amount of ozone emitted by the Ionic Breeze and some other air cleaners.

The report said some ionizers released "potentially harmful ozone levels, especially if you're among the roughly 80 percent of buyers with asthma or allergy concerns." CR gave failing grades to any device with an emission rate higher than the 50 ppb standard used for indoor medical devices. (The Food and Drug Administration does not consider indoor air cleaners to be medical devices.)

The manufacturer says OzoneGuard -- which a company statement says destroys "ground-level ozone by converting ozone molecules to oxygen molecules on contact" -- is not a reaction to CR's May report.

"We continually add improvements to the Ionic Breeze," said Arney. The company had "been looking at ways to reduce trace ozone level emissions, [though] the level was definitely safe before," she said.

OzoneGuard clears some, but not all, ozone in the air; Sharper Image would not provide specific figures for how much ozone is emitted with and without OzoneGuard.

CR reported in May that the Ionic Breeze without OzoneGuard failed a test conducted in a sealed room, but passed when tested in an open laboratory, with readings of 48 ppb at two inches away and 18 ppb at three feet away. With OzoneGuard, the device passed the sealed-room test.

Current Ionic Breeze owners can add OzoneGuard to their units for $9.95 at any Sharper Image retail store or by contacting the company's Web site. All units except the cheapest model ($249.95) have OzoneGuard or can be upgraded to include the new feature. New Ionic Breeze units cost up to $549.95, depending on the size and features of the unit.

CR's report recommends two air cleaners, the Friedrich C-90A (an ionizer) and the Whirlpool AP45030R (a HEPA cleaner). Consumers should beware of false claims and look for air cleaners that report a CADR of 200 to 300, Shaughnessy said, and plug in the unit to see if it has a tolerable noise level.

"Consumers should understand that simply because something is there in black and white," claims made by device manufacturers may not necessarily be accurate, Shaughnessy said. "Consumers have to be very wary of the claims that are purported by all of these product manufacturers."

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On the Web

Consumer Reports www.consumerreports.org; search for "air cleaners"

Sharper Image www.sharperimage.com

American Lung Association www.lungusa.org; search for "residential air cleaning devices"

E-mail: paynej@washpost.com

Sharper Image retooled its Ionic Breeze air purifier, above, adding an "OzoneGuard" grille, inset, after Consumer Reports criticized the model for producing excess ozone. The magazine says the new device still cleans air poorly. Sharper Image says the magazine's evaluation methods are flawed.