There are cheap glass fiber types; media filters of different styles and electrostatic filters in active and passive working modes, that we do not recommend because of extreme low efficiency.
Good Filters will come with some kind of a Rating. Without rating how will you know what to get or how the filter performs? A commonly used Rating is called MERV (Minimum Efficiency Rating Value), we recommend a rating of at least 8 or better 9 to 11.
To find the right filtration for your situation will depend on the location of your filter, the size of the opening and more. As a rule of thumb, for a typical 3-ton HVAC unit, there should be at least 3 square feet of media filter present.
Please call us for all of your air filtration concerns. We offer high performance electrostatic air filters and provide periodic filter service for commercial buildings.