Q. How to I locate my furnace filter or air conditioner filter?
1. Check your mechanical room - the room where all your heating and cooling equipment is kept. This is usually located in a closet, basement, or sometimes the attic. The easiest way to find your "mechanical room" is by turning the fan setting on your thermostat to the "on" position. Listen for the sound of your system's fan and follow it to its origin.
2. In most cases, air cleaner cabinets have a filter that's much thicker or wider than the standard 1" slot. You may not have a thin 1" filter. If this applies to you, then your furnace uses a "media" filter, which fits in a thick air cleaner enclosure.
Common whole house air cleaners are manufactured by Goodman, Carrier, Bryant, Honeywell, Aprilaire, and Lennox. These larger "box-type" media filters are likely to be between 4 and 6 inches in thickness.