A furnace fresh air intake vent is a furnace vent connected to the outside of a home that allows fresh air to enter. The fresh air is then heated by the furnace and distributed through the vents of the home to provide heating throughout the home.
Fresh air intake vents are responsible for up to 90 percent of fresh air entering a home, which reduces the amount of combustion gas buildup. Intake vents typically have a screen attached to help eliminate pollutants entering the house, although traditional screens are not equipped with air filters. As of 2015, newer vents, such as the Ultimate Vent, offer air filtration, heat recovery filters and HEPA air purifiers.