Why are there two air filter slots in my HVAC system?

Your Complete Guide to Furnace Filters furnace filter slot cover Buy AllergyZone FilterLock Furnace Filter Slot Seal Door Cover, 1 at furnace filter slot cover Based on recommendations by the Department of Energy, you should cover and seal your filter slots in order to prevent air leaks In addition to preventing air

duo jokers slot The vast majority of furnace installations are completed with shop-made return boots that incorporate a slot into which the furnace filter is