A Few Important Chimney and Fireplace Terms

How well do you know your chimney and fireplace? While the chimney may look like a simple masonry structure, on the inside are many components that work in unison to keep your home and family safe while enjoying the fireplace or heating stove. During an annual chimney inspection, your chimney sweep may point out areas that need attention like cleaning or repair. 

Essential Industry Terms

Starting from the base to the top, here are a few essential industry terms to help you better understand your chimney and fireplace.

Chimney Foundation – This is the cement base that supports the weight of the chimney system.

Ash Dump – The ash dump is below the firebox. Using a trap-door mechanism, the ash from the fire falls into the dump for easy removal.

Firebox – This is the main part of the fireplace where the logs are stacked for lighting. The surrounding firebrick is made to withstand the high temperatures of a fire. 

Throat – The area between the firebox and smoke shelf is the throat of the chimney. Its narrow, angled design expels the carbon monoxide and other gases efficiently out the flue without backing up into the living space.

 

 

Throat Damper – The throat damper is installed inside the throat. It creates an airtight seal to help prevent energy loss when shut.

Smoke Chamber – Just above the throat in the middle of the chimney, also known as the breast, is the smoke chamber. As the smoke and fumes rise through the narrow throat, it is compressed in the smoke chamber to facilitate a more efficient venting.  

Smoke Shelf – The smoke shelf is located at the bottom of the smoke chamber near the damper. Its purpose is to prevent any downdrafts from interfering with the updraft of smoke and gases exiting the flue.

Flue – The flue is the opening, duct, or pipe that expels the smoke, fumes, and other byproducts out of the chimney. 

Flue Liner – The flue liner is a fire-resistant material that covers the flue. It prevents the intense heat in the fireplace from damaging the masonry walls. It also helps prevent heat transfer to combustible materials. Clay tile, cement, and stainless steel are the three most common types of flue liners.

Chimney Crown – The top surface of a masonry chimney is the crown and typically has a flue pipe in the middle. Its sloped design helps divert water away from the flue.

Chimney Cap – The cap is a covering that protects the flue from water intrusion. Some caps have a steel mesh screen to keep small animals and debris out of the chimney. A cap may also have a spark guard feature to help prevent hot embers from flying out of the flue and onto the roof.

Top Sealing Damper – Some chimneys have a damper installed at the top of the chimney instead of in the throat. It is more effective in preventing moisture intrusion and energy loss when the fireplace is not in use.

Flashing – The flashing is a strip of sheet metal that covers the seam between the chimney and the roof to prevent water leaks.