Sorry if this is too OT, but I can't think of a better forum to ask.
Last year I got two outdoor gas heaters from Costco (the kind that
look like steel umbrellas). Last year both worked OK. This year one
works OK, but the other burns with big yellow flames and smokes like
crazy. In less than a minute, it sooted up the entire underside of the
heat reflector.

I know spiders can get in these things, but wouldn't that just mean
less gas and an a smaller flame? It this thing somehow getting starved
for air? Any ideas on how to go about fixing this or what I can check?
I am pretty handy and careful mechanically. I'd like to get more than
one season out of these things.