Normally we're supposed to be concerned about depleting
ozone levels to the point where we inhabit one big sauna, but according to an investigative piece by the Wall Street Journal (subscription required), household air purifiers which produce
the gas as a byproduct may also pose a significant threat. Studies cited by the Journal suggest that both ozone generation as well as filtration models can emit dangerous levels of the reactive gas, which can be harmful either when inhaled directly or when combined with other common chemicals. While the CSPC is currently studying hard emissions caps to place on these products, California has already taken a first step by limiting purifier ozone output to 50 parts-per-billion starting in 2010. Meanwhile, executives from mall mainstay The Sharper Image are scrambling to discover another gimmicky product they can hang their hats on.