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Inside a Chimney

 a typical chimney system


  A Look Inside Your Chimney

Each element is important to your safety

Modern chimneys are constructed of several materials, but they all share certain basic components and functions. Here is a quick chimney guide to help you understand how yours works:

Basic Function

All buildings use some form of heating system to warm water, cook and provide a comfortable environment when it is cold. Whether you use gas, oil , wood or wood chips to generate heat, you need a venting system to release the smoke, gasses and hot air into the environment safely.

The chimney is the device that draws away all these byproducts of combustion.

The Flue

The chimney is basically a long tube from the firebox (furnace or stove or fireplace) to the outside. At the center of the tube is the flue. A flue can be made of metal or masonry. In fact, there can be more than one flue inside a chimney. Each fireplace and stove usually has its own flue. That’s why you see some chimneys with several smaller tubes extending above their masonry caps.

Flue Liner

The wall inside a flue is lined with material to keep the heat and gasses from getting into the house. Some liners are stainless steel. Others are built of aluminum or terra cotta or cement-like material. Problems occur when cracks or rust cause openings in the flue liner. Heat and gasses can enter the house causing fire or health issues.

Damper

The damper is a door-like device at the base of a fireplace flue. When the damper is opened, air is drawn up into a properly constructed chimney.  When you forget to open the damper before trying to start a fire, the smoke generated by combustion fails to go up the chimney and fills the house.

 Chimney Crown

The masonry covering at the top of a chimney is called a crown.  The crown prevents rain water from running down the inside of a chimney. If there is water inside your fireplace, a broken crown is the chief suspect. The flue extends through the crown.

 Chimney Cap

The cap is a covering at the top of the flue.  It usually contains a screen or wire mesh. The screen prevents hot embers from drifting out and setting the roof on fire. It also keeps birds and critters from entering  the chimney when the fireplace isn’t being used. The cap also prevents water from entering the flue. Specialty caps are also designed to prevent wind from forcing smoke back down the flue and into the house.  These are employed in high wind areas or where roof or  terrain conditions create down drafts.