I could’ve sworn I wrote about this last year when the initial Consumer’s Report article was released stating that all these Ionic air purifiers where actually very unhealthy for you, but I can’t seem to locate the entry and there’s a good chance I never actually got around to writing it. Anyway, back in April of last year the folks at Consumer Reports came out with an article that said ionic air purifiers in general, and the ones marketed by Sharper Image in particular, were bad for you because they produced ozone which could build up in a closed room to unhealthy levels. As you can imagine the folks at Sharper Image were right royally pissed about it and took CR to court over the issue—the case was tossed out by the judge—and then went on to modify their air purifiers with little anti-ozone attachments that you can now see in all their commercials and which are obviously too small to remove all the ozone from the air.

Now a second study from the National Science Foundation and published in the Journal of the Air & Waste Management Association comes to the same conclusion: Ionic air purifiers are your own personal smog machines and should be avoided:

Nizkorodov and colleagues tested various air purifiers in homes, offices and cars. In many cases, ozone levels inside climbed above 90 parts per billion, exceeding California’s basic safety threshold. In some cases, ozone soared higher than 350 parts per billion, which if measured outside would trigger a Stage 2 Smog Alert, an event that hasn’t occurred in the Southern California coastal air basin since 1988.

California lawmakers are considering legislation to reduce emissions from indoor air purifiers. Meanwhile, both the state and the U.S. Environmental Protection Agency have issued advisories discouraging their use.

“These machines are insidious,” said Barbara Riordan, acting chairperson of the California Air Resources Board (ARB), in a warning last year. “Marketed as a strong defense against indoor air pollution, they emit ozone, the same chemical that the ARB and … U.S. Environmental Protection Agency have been trying to eliminate from our air for decades. More chilling is that some people susceptible to the ill effects of ozone will eagerly bring these Trojan horses home.”

Science does not even suggest the things do what they’re purported to do.

An EPA fact sheet has this to say about air purifiers: “Available scientific evidence shows that at concentrations that do not exceed public health standards, ozone has little potential to remove indoor air contaminants. Some manufacturers or vendors suggest that ozone will render almost every chemical contaminant harmless by producing a chemical reaction whose only by-products are carbon dioxide, oxygen and water. This is misleading.”

You can bet the folks at Sharper Image aren’t going to be too happy about this new report. Their website has a whole FAQ on the issue of ozone and whether it’s safe to use their air purifiers from the last report that called their products junk so you can bet they’ll be throwing out press releases like crazy over the next couple of days trying to contain the damage from this latest study. When you consider they charge upwards of $350 for these things it becomes clear why they want to pretend they’re actually worth purchasing.