On Tue, 1 Oct 2013 19:06:20 -0700, "bob" wrote:

If I set up an exhaust fan in the crawlspace that runs non stop, eventually
the motor would wear out and fail.
Would it go up in flame? Or are all motors used in the usa required to
shutdown gracefully?

Alot of fans/motors are used in commercial applications. I can't imagine
them going up in flames at the end of their lives.

Motors I've had fail; generally given early sings / sounds before the
seize up and fail. Never had one catch fire.

Could you use a timer on the fan? Unless you need 365/24/7.