Sounds strange but the very device you put in your master bedroom to clear the air may in fact be creating more pollution.

The Wall Street Journal reports in today's editions that air purifiers may produce a highly-reactive ozone gas, that while being beneficial as a filter of harmful ultra-violet rays, may also be serving as a pollutant on the ground.

Air purifiers have been a source of controversy for years. In 2005, Consumer Reports magazine said that even the best air cleaner can be a frivolous investment and said there was little evidence that the devices will reduce the effect of indoor pollutants for those with asthma or allergies.

"Ozone is considered a toxic gas by the EPA, and its adverse effects include lung damage, exacerbated asthma symptoms and, at high levels of exposure, an increased risk of death," said the WSJ report.

Consumer Reports has reported previously 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.

Consumers have for years reported their concerns about the unforeseen effects of the devices.

"I purchased a Living Air Flair in 2004, thinking that I was doing something good for my family because we lived in Valencia, CA where the air quality is often very poor. We used that machine almost daily," said Lindsey of Lincoln, Calif. "My son developed asthma about 2 months after we started using the machine."

In 2000, a federal judge ordered Alpine Industries, Inc., a Greenville, Tennessee, manufacturer of ozone generating air treatment machines to stop claiming that their machines provide relief from any medical condition or remove a wide variety of indoor air pollutants.

A jury had earlier determined that the defendants' claims that Alpine machines could control the ambient level of indoor ozone using a sensor installed in the machine were not supported by competent and reliable scientific evidence.

The latest report puts another cloud over the popular retail product, which is today sold by many leading online and retail stores, such as Sharper Image and Brookstone.

Five specific products, the Zontec Perfect Air 100, Jenesco FM-1 air purifiers, Friedrich C-90B, the Kenmore K6 85264, and the Honeywell QuietClean, were mentioned in the WSJ report.

Representatives of the air purifier industry defended the products and called for more scientific research.

One manufacturer was quoted as saying that he was aware of the health hazards posed by some air purifiers. He was quick to add that he warns customers that they should turn on the air purifiers in their homes when they are away -- either at work, or running errands on the weekends.

The U.S. Consumer Product Safety Commission, or CPSC, which has jurisdiction over residential air purifiers, hasn't set ozone limits for such devices," the Journal noted.