Direct-vent heaters typically are adjacent to an outside wall and vent through that wall. They have a double-walled vent that permits combustion air to be drawn from outside the space where the heater is located, unlike atmospheric-vent heaters. That ensures that there can be no back-drafting of fumes into a residence, provided that no window is located close to the outlet for the wall vent.

Direct-vents eliminate the need for a vent to pierce the roof and can be useful in snug homes where changes in air pressure by fans cause pilot lights to be snuffed out.