A good way to test if you need to change your filter:
Remove filter (if you don't KNOW where your filter is located check the equipment manual), IF you can hold it up to your face and take a deep breath, it probably don't need changed. If you would't even touch the thing...it needs to be changed!
Furnace filters become dirty during the heating or cooling season as air is pulled through the furnace for circulating through the house. A dirty furnace filter can cause parts to wear out on the furnace and increase energy consumption. Replacement furnace filters should be chosen that meet the needs for the amount of dirt in the air where the furnace is located.
A furnace filter traps airborne particles, such as pet dander, dust mites, pollen, mold spores and bacteria from the air entering the system to prevent the dirt from entering the blower that could increase maintenance. It is easier to replace a furnace filter than to replace worn parts in the blower assembly.
A furnace filter that becomes dirty in less than an average heating or cooling season may indicate poor air quality. It should be checked or replaced depending on the type of filter at least once a month and change them every three months.
Check your filter regularly! Order your filters here.