Consumer Reports magazine renews criticism of Sharper Image's Ionic Breeze Quadra Silent Air Purifier in its May issue.

NEW YORK (CNN/Money) - Shares of Sharper Image fell nearly 9 percent on Tuesday after Consumer Reports magazine renewed criticism on one of its popular air purifiers in its May issue.

The magazine, hitting newsstands on Tuesday, said that Sharper Image's Ionic Breeze Quadra Silent Air Purifier and four other similar air purifiers fail to significantly clean the air -- some can also expose users to potentially harmful ozone levels.

Consumer Reports said it tested ionizing air cleaners for ozone levels and for their ability to remove dust, cigarette smoke and pollen from the air, and Sharper Image's Professional Series Ionic Breeze Quadra SI737 SNX is one of five products that was ineffective as air cleaners.

Four other models included Brookstone Pure-Ion, Ionic Pro CL-369, IonizAir P4620 and the Surround Air XJ-2000.

The magazine also said that people with asthma or respiratory allergies are especially sensitive to indoor ozone, an irritant that can worsen asthma, deaden sense of smell, raise sensitivity to pollen and mold, and may cause permanent lung damage.

The May issue is being published only two months after Sharper Image agreed to pay Consumers Union, publisher of Consumer Reports, $525,000 in legal costs after a federal judge dismissed a libel lawsuit alleging the publisher printed false information in an October 2003 article about the Ionic Breeze's ability to reduce airborne particles.

"It is astonishing that Consumers Union would continue its misguided efforts to attack the judgment and experience of millions of Americans who are satisfied with the performance of the Ionic Breeze products," Sharper Image's lawyer E. Robert Wallach said in a statement.

But Consumer Reports said it stands behind its findings.

The magazine told CNN/Money that "it is ludicrous to suggest that Consumers Union, the nonprofit publisher of Consumer Reports, 'attacks' consumers." "(We) stand by its testing and reporting on air cleaners, (and it) has provided its expert, independent assessment of several air cleaners that claim to trap charged particles on oppositely charged plates."

Sharper Image (Research) stock closed $1.36 lower, or down 8.7 percent, at $14.32 on the Nasdaq.