How Does a Chimney Work?

Today, most chimneys have become redundant due to gas central heating and electric fires. However, in the past, a working chimney was absolutely essential for keeping a home warm. A chimney is based on the principle that hot air rises while cold air falls. A draft will need to be created inside of the chimney for it to work well.

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Inside of the chimney, the air needs to be warmer than on the outside, in order to pull air in from the fire and the cold rooms that the fire is being used to heat. The hotter the air inside of the chimney gets, the stronger the draft will be. The draft will also be greater in a taller chimney.

Chimney drafts create an airflow that acts like a vacuum, drawing out cooler air faster than the ways that it would normally leak out through floorboards, under doors, or through cracks in windows.

Chimneys have become much more complex over the centuries of evolving building design. Early chimneys were just a straight and simple hollow column where the air moved up and out. However, modern chimneys have a number of parts that all work together including flues, flushing a crown, a cap, and many other components.


The flue is a metal plate that is typically located up inside the chimney. It can be opened or closed by pulling a metal chain that extends the chimney length. It is designed to work as an additional sealant layer to keep out cold air when the fireplace is not in use and prevents birds, rodents, and other animals from nesting inside the chimney.

How to Block up a Chimney


A damper is a removable metal plate on the chimney. Opening the damper allows smoke and air to move up into the chimney and outside. Closing the damper prevents air from getting through.


Liners are often installed within chimneys to prevent the materials around the chimney from getting too hot. Since homes often have a lot of flammable materials inside, the liners ensure that the hot air is isolated to the chimney only.

Chimneys will work best when they are properly cleaned and maintained regularly. Oils and gases can build up inside chimneys when left unattended for too long, increasing the risk of the chimney catching fire. Regular cleaning and professional maintenance are the best way to reduce the risk of fire and keep your chimney in a safe working condition.