With more and more people having respiratory problems, whether as a result of asthma, pollen allergies or simply as a reaction to pollutants, air purifiers for domestic use are becoming a big market.

Some of the more common typers of air cleaners use either HEPA filters or ionization technology. Air purifiers which use ionization electrically charges the air particles and draws them to metals plates that captures them, and therefore circumvents the issues of filter-change, motor-noise and draft associated with devices that use HEPA filters.

However, a review of ionizing air purifiers published by Consumer Reports indicate that, ironically, these devices may even aggravate respiratory problems. The root of the problem is that these gadgets emit ozone as a by-product. What's wrong about ozone?

Experts agree that an ozone concentration more than 80 ppb for eight hours or longer can cause coughing, wheezing, and chest pain while worsening asthma and deadening your sense of smell. It also raises sensitivity to pollen, mold, and other respiratory allergy triggers, and may cause permanent lung damage.

According to their survey, only 2 out of the 7 room air cleaners tested performed well in eliminating smoke, dust and pollen. And worse, the 5 poorly rated ones were also found to emit ozone higher than the acceptable levels. And if you think that by getting the more expensive one, you're on the safe side, well, think again. Or better, check out the Consumer Report's ratings for Room Air Cleaners.

You amy also want to read the Washington Post's article, Into Thick Air, or News-Medical's Air purifiers increase ozone levels exceeding health standards.

[Photo: Sharper Image's Ionic Breeze Quadra, costing about $400, NOT recommended by the Consumer Reports ratings]