Fiberglass furnace filters or commonly known as disposable air filters or discount furnace filters are documented to provide less than 8% filtration efficiency. They are specifically suited for pre-filtering or screening out the largest airborne debris, only capturing dirt particles if they directly attach to one of the fibers, therefore allowing other particles to pass right through the open pores.

At some point, if the fiberglass furnace filter is not replaced within 30 days, the captured dirt at the forward side of the air filter will eventually build up to the point where it reaches its maximum limit. Ultimately, causing harm to the air within the home and potentially damaging the furnace unit.

An additional concern that these cheap filters create is what they call “Dust Dumping”. As soon as the furnace filters are being replaced, the collected dirt is dumped and therefore leaving massive amounts of dust particles to be redistributed in the air handling system.

Finally, the fiberglass made furnace filters not only represents a basic pre-filtration air dust filter, the adhesive used for bonding the fiberglass to the panel frame can often act as a growth medium for mold and or microorganisms.