james wrote:
I'm using a $20 household fan 24/7 to ventilate a damp crawl space by
sealing it against one of the crawl space vent (i.e. becomes an exhaust
fan).

Eventually this fan is going to fail, perhaps the bearings wear out and
then the fan stop spinning.

Should I worry about a fire, or do all UL listed fan have some sort of
overheat protection?

Is there some sort of fan that is designed to run 24/7 and is well
protected against overheating?

I read of household fans being a fire hazard long time ago. Only reason
I remember is because my hubby likes to leave them running, 24/7, even
when the room is not occupied.

If you are planning a permanent installation, then find a fan built for
the purpose that runs on a timer. Constant circ. seems a waste - just
periodic to sufficiently move the air. Is the crawl space sealed up
with moisture barrier?