Stupid spray booth question

I wouldn't!  While the fact that you have a fan in the exhaust indicates a high efficiency furnace and the temperature is thus low enough it probably wouldn't ignite dried paint, I still wouldn't chance it.

I find that a filtered booth cuts down a lot on the fumes.  The filter collects the paint particles and they seem to outgas more slowly when stuck on the filter than they do in the air. Probably less surface area.   I see two purposes for a spray booth- cutting overspray in room, and reducing fumes/smell.  The filtered booth with no outside vent certainly fulfills the first purpose, and does help some with the second.

Don Stauffer

I wouldn't!  While the fact that you have a fan in the exhaust indicates a high efficiency furnace and the temperature is thus low enough it probably wouldn't ignite dried paint, I still wouldn't chance it.

I find that a filtered booth cuts down a lot on the fumes.  The filter collects the paint particles and they seem to outgas more slowly when stuck on the filter than they do in the air. Probably less surface area.   I see two purposes for a spray booth- cutting overspray in room, and reducing fumes/smell.  The filtered booth with no outside vent certainly fulfills the first purpose, and does help some with the second.

Please recall, I specifically specified that it would be used in the summer, when the furnace wouldn't even be in use, and that the furnace doesn't even have a pilot light.

I just cut a 4" hole in the siding, between the floor joists(basement ceiling), plugged it up with a dryer hose/ flapper vent.

I thought about something along those lines but the more I looked at the brick on that side of the house, the less I wanted anything to do with it.

No- I would not recommend messing around with your furnace in any way!  They are engineered to work as they have been designed, any modifications like this might be dangerous.

Just for clarification, it would not be messing with the furnace, but tapping into the exhaust vent, in the same way that a NG hot water heater will also tap into the same exhaust vent.