Just the faint smell of activated carbon that u could only catch a whiff of if u put ur nose to the edge. even I f ur filter "expired" I would think that molecules would dissipate so there would be no strong aroma by the time it hits ground level. Make sure U mask the light coming out of the chimney. U'll mess around and look like ur callin Batman, but I bet he's not the gonna be the 1 knockin on ur door. But I'm speaking theoretically. Filter + chimney exhaust =
and the u can go on vacation and
