Air Filters: Options for Improving Air Quality

Air filters are not only available in a variety of styles but with a large range in efficiency at filtering "offending" particles that are suspended in the air. Ranging in price from the extremely economical standard fiberglass furnace filter to the high-end high quality HEPA filters, the choices can be somewhat confusing if not downright overwhelming.

Air Filters versus Air Purifiers

A true air filter is designed to purify the air by physically removing particles such as dust, pollen, mold, bacteria, and viruses. Air purifiers are not true air filtration devices; purifiers perform a cleaning function of the air either by inundating particles with ozone or by binding them with negative ions. Two popular "true" filters are electrostatic filters and HEPA filters.

Electrostatic Filters

Electrostatic filters use a static charge to attract particles to the filter. They are reusable as the dust and associated particulate matter can be rinsed off. While they can filter nearly 90% of the particles that eventually pass through them, their efficiency at filtering microscopic-sized (less than 35 microns) particles is approximately ten percent.

HEPA Filters

HEPA filters (high efficiency particulate arresting/arrestance/accumulating/absorption/air - depending on which definition you choose to use) are generally found within systems that use a fan to draw air across the filter and then release the cleaned air back into the room. To be labeled a HEPA filter, the filter must be capable of removing at least 99.97% of all airborne particulate matter that measures 0.3 microns in size. To put that into perspective, pollen is 10-100 microns and dust is 0.5-5 microns. While HEPA filters must be replaced on a regular basis and are generally more expensive to purchase and operate, they are considered to provide the highest quality of air.