Don’t light that fire just yet
When the temperature drops, you want the cozy comfort of a working fireplace. But before you light that match, there's one essential step you can't skip: opening the chimney flue. It ensures that smoke and harmful gasses escape your abode and your fire burns efficiently. If you're unsure what to do, we explain how to open a chimney flue.
Homeowners typically keep their chimney dampers closed when the fireplace isn't in use. In the winter, this prevents heated indoor air from escaping and blocks cold air from creeping inside. However, when a fire is burning, you'll want the damper open to direct the smoke up the flue and out of the chimney. In short, the key to opening a chimney flue is simply opening the damper.
Opening a chimney flue involves testing to see if the damper is open or closed; looking for the lever, handle, or chain that controls it and determining how it works; and testing the air flow. Here’s a closer look at the steps involved.
You can do a few things to determine if your chimney damper is open. First, put your hand in the fireplace and check for cool air coming down from the chimney. If you feel a chill, the damper is most likely open.
You can also try looking up your fireplace with a flashlight. Before doing so, wear your gloves, mask, and safety glasses to protect yourself from soot. You will find the damper above the firebox, and it typically resembles a small metal panel or door.
If you are still uncertain, light a match or make a very small test fire using a piece of paper. If you notice that the smoke is not going up the chimney, the flue is closed.
Discovering what opens the damper is a straightforward process. Look for a lever, handle, or chain that controls it. In older homes, these controls are typically found inside the fireplace, near the top of the firebox, or just above the fireplace opening.
The lever or handle is usually a rotating mechanism that moves side to side or up and down.
Once you've located the control, gently test it to see how it operates. Using a glove-covered hand or fire poker, try moving the lever in different directions—usually, one direction will open the damper while the opposite will close it.
In newer homes, the damper's open and close switch may be found on the hearth near the fireplace opening.
After you've opened the damper, it's time to test that the flue is fully open and functioning as it should. One effective way to do this is by testing the airflow. Begin by lighting a small piece of paper or a match and holding it in the firebox below the damper. Watch the smoke—if it rises steadily and quickly draws up the chimney, the flue is open and allows proper airflow.
However, if the smoke lingers around the fireplace or starts to drift into the room, this suggests that the flue may not be fully open or there might be a blockage in the chimney. In such a case, you should recheck the damper's position. If the problem persists, consider having your chimney inspected by a local chimney repair specialist to rule out any obstructions in your chimney flue.
Opening or closing a chimney flue is generally a simple task most homeowners can handle.
However, there are situations where hiring a pro might be the better option. If you’ve recently moved into a home and are unfamiliar with the fireplace setup, if the damper mechanism is stuck or difficult to operate, or if you suspect there might be a blockage or damage in the chimney, it’s a good idea to call a chimney professional. A chimney inspection costs around $450.
Yes, it’s essential to clean creosote from your chimney flue annually—although this is typically a job for a pro, not a DIYer. Creosote is an extremely flammable substance that builds up from burning wood in your fireplace. Over time, it can accumulate in your flue, increasing the risk of a chimney fire. Regular cleaning by a professional chimney sweep removes this dangerous buildup, ensuring your fireplace operates safely and efficiently.
Yes, if your gas fireplace has a flue, you typically need to open it when using the fireplace. Although gas fireplaces don’t produce the type of smoke and soot that wood-burning ones do, they still release combustion gasses like carbon monoxide. Opening the flue ensures these gasses safely exit your home through the chimney. Not all gas fireplaces need a chimney, however. Always check the manufacturer’s instructions for your specific gas fireplace model, as some newer models may have different ventilation requirements.
