The good news is that most air purifiers do purify the air. The bad news is most people derive little to no benefit from their use. Using air purifiers as part of a multi-pronged attack against allergens or pollution seems to be the best route to take, but the effectiveness of air purifiers alone is considered by consumer advocates to be negligible. Considering the average price of high-end air purifiers offered through specialty outlets such as Sharper Image or Brookstone, other less-expensive air treatments should most likely be considered first.
Air purifiers work in a number of ways, but quite commonly the purification mechanism is an electrostatic charge on metal plates. The entire unit is placed in a inconspicuous location and air naturally circulates through it. As the air passes over the charged plates, any dust or spores or other floating debris should be captured by the electrostatic charge, much like salt crystals being attracted to a statically-charged comb. The air coming out of passive air purifiers should be much cleaner than the air going into the unit.
The problem with passive electrostatic air purifiers is that many common allergens do not float in the air because they are too heavy. These allergens and germs remain on the ground or other surfaces and rarely if ever reach the electrostatic plates of air purifiers. Air purifiers also take allergens and harmful germs out of the air, but then cause them to fall onto carpets, furniture and clothing. The plates themselves must be removed periodically for cleaning, which could expose the user to more allergens and bacteria.
Air purifiers containing motorized fans do offer some advantages over passive models. More air can be treated if it is drawn into the unit mechanically. Air purifiers can also keep the air circulating, which keeps dust and allergens from landing on other surfaces. If a person required more purified air due to a health condition, air purifiers with special HEPA (High Efficiency Particulate Arrestor) filters could work well in conjunction with other air filtration systems.
One of the major problems associated with air purifiers is the production of a heavy oxygen gas known as ozone. Ozone in the atmosphere serves as a protective layer against harmful solar radiation, but concentrated ozone in a confined space can cause a number of serious health problems. Many air purifiers using electrically-charged plates do generate ozone as part of their process. The health benefits of purified air may not be enough to overcome the potentially harmful effects of ozone-producing air purifiers. Consumers should look for HEPA filtration, low ozone production and some form of air circulation when shopping for air purifiers. The passive electrostatic air purifiers may offer some piece of mind, but very little actual health benefit.