Why Is Smoke Coming Back Into My House From the Fireplace?

A fireplace that sends smoke into the room is telling you something is wrong with the relationship between the fire, the flue and the air in the house.

Sometimes the cause is simple. Other times it points to a venting, sizing or pressure problem that needs a closer look.

Start with the damper

For a traditional open fireplace, make sure the damper is fully open before lighting the fire. A partially closed damper can restrict the path smoke needs to follow.

If the damper is difficult to operate, rusted, broken or not opening fully, it may need repair.

A cold flue can resist draft

Chimney draft depends in part on temperature difference. When the flue is cold, especially after sitting unused, a column of cold air can move downward or resist the upward flow of warm gases.

Once the flue warms, draft may improve. But repeated severe smoke spillage should not be dismissed as “just a cold chimney,” especially if it did not happen in the past.

The home may be competing for air

A fireplace needs air for combustion and draft. In a tight house, powerful exhaust equipment can pull air out faster than replacement air enters.

Common competitors include:

• Kitchen range hoods
• Bathroom exhaust fans
• Clothes dryers
• Other vented combustion appliances

If smoke spillage changes when these devices are turned on or off, pressure should be considered as part of the diagnosis.

The flue may be blocked

Nesting material, leaves, debris, damaged components or heavy deposits can reduce the effective vent area.

A chimney cap helps keep larger debris and animals out, but caps themselves can become damaged or obstructed.

Wet wood creates more smoke

Wood with high moisture content is harder to burn cleanly. EPA guidance recommends seasoned firewood and notes that wood burns best at about 20 percent moisture or less.

If you are fighting to keep a smoky fire alive, the fuel may be part of the problem.

The fireplace and flue may not be well matched

Chimney height, flue area, fireplace opening size, appliance type and installation details all influence draft.

Problems sometimes appear after a fireplace is modified, an insert is removed, a new appliance is connected or a chimney liner is changed.

A system that “worked before the remodel” but not after it should be evaluated as a whole rather than treated only with cleaning.

Wind and chimney termination can matter

Wind moving over a roof can create changing pressure around a chimney. Nearby rooflines, trees or additions can alter airflow patterns.

That does not mean every smoky fireplace needs a taller chimney. Termination height and draft modifications should be evaluated against code requirements, the appliance and the actual cause.

What not to do

Do not keep using a fireplace that repeatedly fills the room with smoke and simply open a window as a permanent solution. Opening a window may temporarily change pressure, but it does not tell you whether the chimney is blocked, damaged or improperly configured.

Do not burn accelerants or build an oversized fire to “force” the chimney to draft.

A useful diagnosis asks several questions

• Did this start suddenly or has it always happened?
• Is it worse in certain weather?
• Does it change when exhaust fans run?
• Has the home been remodeled or air-sealed?
• Has the appliance or insert changed?
• Is the wood dry?
• Is the flue clean and unobstructed?
• Is the chimney damaged?

The answer may be one issue or a combination.

If your fireplace is smoking into the room, Keaton Chimney Solutions can inspect the chimney and fireplace system throughout Denver, Colorado Springs, Fort Collins and surrounding communities. Call 720-734-5373.

Need help with a chimney or fireplace in Colorado? Keaton Chimney Solutions serves Denver, Colorado Springs, Fort Collins, and surrounding communities. Call 720-734-5373.