According to Wade :
You all have me on both counts. I do have more dust in the house than I
should and my wife does burn candles from time to time, so I guess it's time
to do some major cleaning. Thanks, I was more focused on the bulbs
themselves and not the quality of air in the house.

I'll add one comment - I think it's moderately unlikely that hot lightbulbs
will cause blackspots on the ceiling due to atmospheric dirt and heat
upwelling _alone_. Certainly not with any great rapidity, even with
vast quantities of grease in the air (which'll make the stuff stick).

If these fixtures are suspended from electrical boxes in an attic
ceiling, the boxes themselves are probably leaking warm air like
crazy into the attic, which will _greatly_ increase the total airflow
and crud deposition rate. Especially if there's any condensation there
(some of the black could even be mould).

So, while you're killing yourself cleaning up the house ;-), a short
amount of time bagging the fixture boxes (from the attic side) with
vapor barrier plastic may be time well spent.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.