If you have gas logs (or decorative glass, rocks, etc.) installed in your fireplace, this is not an uncommon problem. Per uniform building code requirements, when there is gas plumbed to a fireplace a damper clamp must be installed to keep your damper from closing. If the gas line is capped off and no log lighter is installed, then is permitted to be functional.

Another common problem with dampers is that they become stuck or frozen into position. In such cases, lubrication can be helpful.