Ignoramus23561 wrote:


After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.
Wow, this is one of the most scary sorts of electrical problems, the
latent high-resistance short. Fortunately, in this case, if it happens
in the dangling cords, it is at least somewhat likely to turn into a
major short and trip the breaker before it spreads. But, you are
right, you should examine all of these connectors for dust and any
other deterioration. I'd turn off breakers to every unused receptacle,
and then only turn them on as you get them cleaned out. It may also be
there's a lot of dust in the junction boxes up on the ceiling, too, and
maybe in every other electrical box and panel.

Ugh, this might be a mess to clean up!

Jon