Had never occurred to me, but it seems like a remote possibility. There's a lot of glue in particle board.
A coat of latex paint would seal it up, I'd think.
You might try using a lot of ventilation to see if it clears up.
That sounds a lot better. If you try to blow air into the furnace exhaust there's a chance you'd reverse the flow in the exhaust and force it out the furnace body, potentially causing CO to build up in the furnace area
The spots look like a micronutrient deficiency to me. If you've been using pure distilled water, that would explain it. If you're using well water, I'd assume it has micronutrients already, in which case it's probably a ph problem.
In my experience it's hard to get a good ph reading on water...