A throat damper is a metal door located above the firebox, but below the flue pipe. (See a diagram of the parts of a chimney here.) When the damper is closed, it slows the loss of heat that would otherwise go up the chimney. When it is open, it allows smoke and exhaust gases from the fire to escape up the chimney. A handle beside or just inside the fireplace operates the damper.
If you start a fire before opening the throat damper, smoke will flow out of the fireplace instead of going up the chimney. Worse yet, if you have a gas fireplace, burned gas can escape the fireplace and create the conditions for carbon monoxide poisoning.
How to Open Fireplace Damper
You can easily check to make sure the damper is open by looking up the chimney with a flashlight. If the damper is closing off the flue, use the handle to open it. When you operate your throat damper, be sure to use a pot holder or pliers in case it is hot.
To open your fireplace throat damper
- From the starting position (1) …
- Lift the handle (2),
- Push it forward (3) , and
- Latch it by pulling down (4).
To close the damper
- Lift the handle and
- Pull it back toward you.
More on when (and why) to close your damper.
When you look up the chimney, you will see a flat, rectangular steel trapdoor. That’s the throat damper. It has short rods on each end that fit into holes in the sides of the chimney. In most cases, you can remove the throat damper by removing the cotter pin that attaches the handle to the damper plate and then lifting the damper plate out of its mounting holes.
Before lighting a fire you may need to warm the throat damper area by burning some twisted-up newspaper near the top of your firebox in order to get the upward flow started. Once the fire is burning and a good draft is established, close the throat damper slowly, (this applies to wood fires only, not gas!) but not to the point that the fireplace gives off smoke. This step will reduce the volume of heated air that escapes your house along with the exhaust gases. You may need to open the damper again as the fire burns down and the upward draft slows.
When to Close Fireplace Damper
Close the throat damper after the fire has cooled completely. Doing so will keep some of the warm air from your heating system from escaping up the chimney. However, most throat dampers allow some heat to go up the chimney. To improve the energy efficiency of your home, remove the throat damper and replace it with a top damper. Top dampers attach to the top of your flue and completely close off the flue. There’s a stainless steel cable that runs down the flue to a handle located inside the firebox. You can open and close the top damper by means of the cable.
See How to Fix a Stuck Damper.