How to Choose the Right Air Filter

Source: http://www.starqualityair.com
Date: October 13, 2010

The air filter in your home’s air conditioning system is extremely important but is often neglected.  In order to ensure proper filtration you need to think about 3 things: correct filter size, MERV ratings, and your individual needs.  For example, do you have pets? or allergies? Would you prefer disposables or a permanent filter? There are many types of air filters available but once you decided what fits your family the most, it’s really simple.

The first step is to make sure that you know the correct filter size for your system.  Using a filter that is too small or too big will not filter properly.  Air pressure inside the system presses the air filter against the frame of the filter slot which acts as a seal so that air will not leak around the edges.  All you have to do is make sure that the filter size fits into the slot and is large enough to touch all four sides of the frame.

You can usually find the nominal filter size printed on the filter itself.  It is important to remember that the nominal filter size is not the same as the actual filter size.  The nominal dimensions are usually slightly larger than the actual filter dimensions.

The next step is understand how filters are rated.  The MERV (Minimum Efficiency Rating Value) developed by ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers) is an industry standard rating system that allows you to compare filters made by different manufacturers. The rating scale values range from 1 (lowest efficiency) to 20 (highest efficiency) and represents how well the air filter collects and holds particles of a specified size range.

Finally, when choosing the proper air filter for your home you must decide if you prefer a throwaway filter, a washable/reusable filter, or an electronic air cleaner.  Disposable air filters are generally inexpensive and need to be replaced every month to three months depending on the filter and the environment in the home.

Washable filters are a little more costly upfront but they can be reused for a number of years before replacing.  These filters are designed to be cleaned/washed every month to three months.

Electronic air filters are permanent fixtures in the heating and cooling system and require an electrical connection.  They are more expensive than any other type of air filter but are very effective at removing particles from the air. Electronic air cleaners polarize the air particles and collect them on a disposable low-static polarized media pad.  To ensure long-term effectiveness, you must be regularly clean the unit and replace the filter pads.