Found this at today’s inspection on gas furnace vent in basement. I’m not sure if the water heater used to be connected here, or if it’s put there to help the booster fan. It’s a flapper, so it opens when the heat runs and the vent blower kicks on. The vent doesn’t extend past the roof, it terminates at ground level, with the vent booster fan assembly just on the inside of the termination point outside.
Is this supposed to be for fresh air? I was concerned with possible CO.
Also, I’m not sure if the vent needs to extend past the roof line, since it has that booster fan on it?