Clearing Your Air With HEPA Air Filters

Whether they're integral components of a home air purifier or additions to your furnace, HEPA air filters are vital to any attempt to maintain your indoor air quality. HEPA is short for High Energy Particulate Air; these filters have, in the past decade or so, become the standard by which air filtration systems are judged. Systems fitted with HEPA filters will strain out just about every particle of dust, pollen, mold, pet dander, and smoke, trapping it until it can be dealt with later.

Do my filters really need to be HEPA?

Filters in most modern air filtration systems are intended to be of the HEPA variety, whether you're talking about furnace air filters or the ones in standard house purifiers. The typical purifier or furnace filter consists of a bed of fibers that easily pick up an electrostatic charge as air flows through; as a result, allergens and other tiny particles are attracted to the fibers and stick there, safely sieved out of the air. Others use microscopic pores to filter out dust and other materials; the air goes through, but the junk doesn't.

How effective are they?

Originally designed during World War II to remove radioactive dust from the air, these high energy filtration systems are the most efficient known. A "true HEPA" quality filter can filter more than 99% larger than 0.3 microns (0.00001 inches) across, and is 95% effective on particles down to a third that size (0.1 microns). A human hair, by contrast, is about 70 microns wide. Several true filters used in series can capture virtually everything; the best HEPA purifiers can even eliminate particles as small as viruses.