What is a Smoke Chamber?

In your masonry fireplace, there is an area called the smoke chamber. In most fireplaces, it can be viewed by shining a strong light up through the damper. Its function is to safely transition smoke and hot gases from your fireplace to the narrow flue of your chimney.

Roughly the shape of an upside-down funnel, the smoke chamber starts just above the damper and ends where the chimney begins. The brick along the sides of the smoke chamber is often stepped outward one above the other, upwards until they meet the flue. This is a process called “corbelling”. The corbelled brick in your smoke chamber will look like an upside-down staircase. Exposed corbelling increases smoke turbulence and reduces the efficiency of the smoke chamber. This allows dangerous creosote and soot to build in the smoke chamber and flue liner. To protect the integrity and increase the efficiency of your smoke chamber, the corbelled areas and any gaps, cracks or jagged edges should be coated and parged smooth with an insulating high-temperature mortar such as Chamber Coat.


The portions of a masonry chimney that aren’t seen can be loosely constructed (shown in the photos below) If an ember finds its way through holes in the smoke chamber, it can escape the chimney completely through these gaps in the masonry. Outside of the masonry, the ember can ignite the wood structure of your home.

These pictures were taken at a fire investigation we were called out to. The homeowner stated the fire had gone out around 9 PM, however, they were awoken to the sounds of fire alarms at 2 AM Christmas morning and had to rush out of their home. Thankfully, everyone made it out of the home safely and the fire department was able to save the majority of the structure.



Fact: There are over 22,000 structure fires a year that start from the chimney, 40% of those start as a result of poor smoke chamber construction.

According to the National Fire Protection Association (NFPA), defective smoke chambers are the third leading cause of chimney-related house fires.

This is why it is important to have your smoke chamber repaired or brought up to code by an expert fireplace repair technician. Butler Chimney’s repair technicians are highly trained and thorough. We will make sure that everything is done to the highest possible standard using the best materials available to our industry.

Taking your smoke chamber from unsafe….


To code compliant and safe in one day.