Traditional Fiberglass or Polyester:

These inexpensive, disposable, 1" filters are recommended to be changed monthly. Because their main purpose is to protect the heating and cooling system from damage, their media is dense enough only to capture large particles. This filter type is not very effective at capturing smaller, respirable particles from the air.

Washable/Reusable:

These 1" filters are designed to be washed out monthly and reused. While this filter is initially expensive, it can be used for a number of years before needing replacement. Tests show that this type of filter is not very effective at capturing smaller, respirable particles from the air. Although some brands of this filter type claim an electrostatic charge created by the air movement through the media, the charge is actually minimal and plays little or no role in particle capture.

Ordinary Flat or Pleated:

It is recommended that these disposable, 1" filters be changed every 2 to 3 months. These filters are generally made out of cotton or polyester media which is denser than fiberglass and will typically capture more small particles than either fiberglass or washable/reusable. The filters can be found with either a pleated or flat media.

Deep Pleated:

The previous 3 types of air filters are 1" deep and can be used interchangeably. Deep pleated filters are either 5" or 6" deep and thus can only be used on heating and cooling systems that are specially adapted to accept them. This filter type may have a reusable frame and the media needs to be replaced once or twice a year. These filters have been shown to demonstrate a broad range of efficiency levels between various brands. The efficiency of some brands is only slightly higher than that of fiberglass while others approach the performance of a permanently charged electrostatic filter.

Pleated, Permanently Charged Electrostatic:

These 1", disposable filters need to be changed only once every 2 to 3 months. Like the four previously mentioned filter types, this type is also designed to physically capture particles. But its efficiency in trapping smaller, respirable particles surpasses both the other 1" air filters and most of the deep pleated filters because its electret fibers are electrostatically charged. Particles which would otherwise have passed through, are "magnetically" drawn to the filter. This filter type represents an alternative to the more costly electronic air cleaners for households trying to improve their indoor air quality.

Electronic Air Cleaner:

This type of air filter is a permanent fixture in the heating and cooling system and requires an electrical connection. Although it is significantly more expensive than any other type of air filter, it is very effective at removing particles from the air. However, it must be disassembled and cleaned regularly to keep its high level of effectiveness. Also, these air cleaners may emit ozone, which can be harmful.

Information provided by 3M.