It is one of the most valued features in our homes. And all too often, the fireplace is labelled “non-working” and sits unused, because the homeowner doesn’t know what to do about a smoking problem. Here we will show how most smoking problems can be handled relatively easily, with little or no expense. Here’s a trick for monitoring smoky fireplaces: If you can’t see the smoke spilling from the fireplace, shine a flashlight across the fireplace opening. The light reflecting off the smoke particles will make it easy to see.

The most common smoking troubles occur when the fire is first lit. If your fireplace smokes only during startup, but is okay after that, here are some possibilities:

Cold Flue: The flue will be cold when you first open the damper. This is especially true in fireplace chimneys built on the outside of the house, rather than up the middle of the house. A tall column of cold air in the flue will tend to sink, causing air to move down the chimney and into the house. So if you open the damper and feel cold air coming down the chimney, don’t light the fire! If you do, smoke might be forced back into the house. What you need is a tall column of warm air in the chimney. So first, prime the flue.

Chimney is Too Short: Wind patterns around a house create pressure zones against the roof. Wind-driven pressure zones are a complicated science, but basically, if the chimney is not tall enough, a pressure zone created by wind will engulf the chimney top, forcing wind-driven smoke down the flue and into the house.

No Chimney Cowl: chimney is an open cavity leading into your home. As such, all chimneys should have caps. A good chimney cap, constructed of stainless steel, copper, masonry, stone, etc, will not only prevent rain and snow from entering the flue, but will also help with certain wind- driven draft problems.

– Roll up a piece of newspaper, light one end, and hold it way up in the damper opening. You might need to burn two rolls of paper. In a minute or so, you will feel the draft reverse, as the warm flue gasses start to move up the flue.
– Once you have primed the flue, you can light the fire.

Blockage: Sometimes, a smoking problem is caused by a partial or complete blockage of the flue.

Depressurized House:  Although this problem sometimes only shows up when the fire is burning low, for some super-tight houses it is a constant problem. This is the first possibility to explore if you have a tightly- insulated house, an air exchange system, or exhaust fans in operation. If there is not enough air available in the house to allow the fireplace to draw, it will smoke. See the explanation and solution in the Smoky Endings section.

Smoke Chamber is too small: The triangular cavity (above the damper) that funnels the smoke up into the flue liner is called the smoke chamber. While an oversized smoke chamber can lead to difficulty in getting the draft going, if the smoke chamber is too small, smoke sometimes curls out at the top of the fireplace opening and spills into the room.
When the fire is out, open the damper and shine a flashlight up into the smoke chamber