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How often should I change my furnace filter?


clean and dirty filters

You may have great personal grooming habits, and keep your home impeccably clean, but how clean is your furnace filter at this moment? In the image above, a new furnace filter is seen on the left, and a used filter (that was probably only 3 months to a year old) is on the right  You’d probably cringe if we told you that dirty furnace filter came out of your basement, but might not worry too much about its effects (other than being pretty disgusting to look at).

Some people think the only result of a dirty filter like this is a slight reduction in effectiveness of your furnace or air conditioner. While system inefficiency is certainly one of the main results of a dirty filter, when the filter becomes so clogged with layers of dust and grime that air flow is severely limited or even cut off entirely, pressure begins to build up inside the furnace. Over a period of time, this increasing pressure becomes so great that it can even result in an actual crack in furnace (yes, on the metal parts).

crack in furnace


This image shows a fissure in the wall of the furnace that was about 2-3” long.  Any furnace that shows a crack like this needs to be replaced immediately—there is always the danger that carbon monoxide can escape into the home, and most of us are not willing to take that chance.


If you have pets that shed dander and fur, or keep your windows open a lot, you may need to check the filter more often than you might think. So maybe it’s time to clean up your act a little and take a quick look at the condition of your furnace filter. Or if you’re the kind of person who is more comfortable leaving this sort of work to the professionals, give us a call at 317-753-0279 and we’ll be happy to take care of it for you.