If you were thinking about buying an air purifier

Maybe you should read this first.

The conlcusion that the article doesn't (but should) draw is that if you're going to buy an air purifier (like the Sharper Image Quadra), probably you should just save your money. There are two ways that these things fail the consumer.

The ozone generators, which specifically generate ozone to purify the air, are really not great for you, and they don't remove particles from the air. As Dr. Nizkorodov notes, "at the concentrations you need to destroy germs and pollutants, the ozone levels are so high you cannot safely use it." If it can kill the germs in the air, what do you think it's doing to your lungs? This could be particularly dangerous for people who want to purify the air in their house because they already have breathing problems.

The ionic purifiers (the Quadra is the most famous) don't make much ozone at all, and you can use them in a large, well-ventilated room without creating dangerous ozone levels. Their ozone is the byproduct, not the intended product. The problem with these air purifiers is that the rate of air flow through the thing is far, far lower than the rate of ventilation (exchange rate) in most rooms. This means that you get dirty air from the outside a lot faster than you get clean air from the purifier. Any particles that the thing removes from the air are just getting replaced; also, certain chemicals in the air (like terpenes) can react with the small amounts of ozone produced to actually make more particles (called Secondary Organic Aerosols).

If you can actually see the air in your house and you really, really need an air purifier, get a HEPA filter. They're more expensive, but they're the least useless (and not dangerous). Overall, I'd say to save your money.

Cross-posted at The Disgruntled Chemist

Tags: air purifiers, Sharper Image, ozone,air pollution, UC Irvine