Coal Stove Stopped Venting Outside

Someone was smoking a cigar in the basement and had a box fan in the window. It didn't occur to me that it could be sucking air from the stove, but the stove was out so that must have been the path of least resistance. I do have a carbon monoxide detector next to the stove and near the bedrooms, so I know there has been no issues when the stove was lit. I'll be monitoring this issue - and asking the cigar smoker to open a window so this doesn't happen again.

Better yet, smoke that stinky cigar out doors or not at all !!

Greg L.