Consumer's Guide for Air Purifiers

Room Size

• You need to know the size of the room in which you want the air purified. For instance, if your bedroom is 13 by 12 feet, you want a purifier that can handle 156 square feet.

Clean Air Delivery Rate

• If the purifier's capacity is not listed by square footage, it might be expressed as a Clean Air Delivery Rate figure. Multiply the CADR by 1.33 to get the square footage the unit can handle (A CADR of 120 would be suitable for the 156 square foot room.)

Round Up

• Keep in mind that square footage and CADR numbers assume the unit is on maximum power, so it's always best to choose a purifier that can handle a bigger room than you need.

High Efficiency Particulate Air Filters

• You should also look for a purifier that uses a HEPA (High Efficiency Particulate Air) filter, which removes 99.97 percent of allergens.

Filter Life

• You should also consider how long the unit's filters last, as most must be replaced after a period of time. The expense of having to change them regularly can add up.