Our woodburning fireplace has no doors or mantle. This year, the front of the chimney above the firebox becomes very hot. The heat ends at the picture hanging 3 feet above, and the bricks behind that picture are cool. The heat stops at that line. The co2 alarm, which is in the hallway and not near the fireplace, does not register anything. No smoke is getting in the room.

I don’t remember this happening in past years.