I have a Keystoker (90KBTU, Hearth model) running for its fourth winter. All has been well, until recently I've been getting an odd chemical smell in the house, intermittently on different days. It's definitely not sulfur/combustion gases...very different smell/CO alarm is quiet...and it's not the beginnings of a hopper fire. Draft is good, clear chimney, etc. Rather, it seems to be a hot oil smell and there's a very faint visible vapor coming off the coal in the hopper. I believe that there may be some contaminant on the coal as some of the coal in the hopper appears wet or oiled, even when it's been in the hopper for hours. It's not wet with water.
This morning I scooped out the 20 pounds or so of coal in the hopper and the vapor continued to come off it until it cooled. I'd guess the coal was 150 degrees F as I could put my hand in it, uncomfortable but not burning hot. Again, there's not an over-temp problem in the hopper. Just very warm from being close to the firebox. I'm burning bagged rice coal from Blaschak.
I'm guessing a few bags worth had some oil or other contaminant spilled on them. Anyone else have similar issues?