The Case for a Return Duct Filter Regular maintenance is certainly recommended, but adding a return air filter can help to block some of this incoming debris and ensure that the air coming in is clean. Clean air means a clean system.Click to see full answer. Accordingly, are vent filters a good idea?Most vent filters are designed to be less effective than HVAC filters overall, but strong enough to block larger debris, prevent insects from crawling in and out of vents, and make it easy to recover small items dropped into a vent. Do you, however, need a vent filter to reduce the amount of allergens in the air?Similarly, are return vents important? While supply vents blow out conditioned air, return vents are just as important to your home’s overall comfort and a properly functioning AC system. Instead, return air vents suck the air from your rooms into your return ducts and back to your heating and cooling system. Secondly, where should the return vent be located? Place your cold air return vents on the inside walls of buildings at the lowest point. The return vent pulls cold air from the bottom of the room and returns it to the furnace to be reheated and returned as warm air. Unlike supply vents, return vents do not need to be cased in metal.Can you put filters in vents?Do not put filters in your supply vents. Your AC system should have a proper fitting filter on the return side. By placing a good fitting, high quality filter on the return vent, you will remove particles from the air before they can enter the AC system.