Chimney Terminology Section:
Throughout this website, there are specialist words or terms used frequently that this page seeks to clarify for our website readers. We appreciate that some of these terms may have alternative meanings, however, please take our explanations in the context of this website.
Air Vent: Also known as an air duct. This is an opening which allows air to enter or leave the room where the heat producing appliance is.
Boiler: Closed burning appliance designed to transfer heat through combustion to water, which in turn, is used to heat a remote part of the dwelling. They are designed to burn various fuels. See Central Heating.
Capping: Also known as a Crown (in North America). It is the top of a masonry chimney that surrounds the flue opening or ceramic liner. Usually constructed from concrete to provide a robust waterproof protection.
Central Heating: A terms used to describe the process by which a boiler or furnace distributes heat throughout the dwelling. Please see Boiler explanation.
Ceramic Liner: A type of protective tubing used to line a chimney internally. They are usually round in Ireland and Great Britain. In North America, a ceramic liner can be round, square, rectangular or oval. Manufactured from heat resistant fire clay.
Chimney Breast: A section of a building that contains the chimney shaft or shafts. Chimney breasts can be visible, i.e., proud of the wall or invisible and contained inside the wall.
Chimney Cowl: Also known as a cap (in North America). It is placed on top of a chimney. They are used to prevent moisture, birds or wind entering the chimney (down draught). Chimney cowls can be also used to increase or decrease draught.
Chimney Fire: This is when the inside of the chimney, normally the lining, catches on fire. The temperature rises very rapidly, and the structure of the chimney can be damaged. Often caused by nesting material or creosote catching fire. In the resource section of our website, there is an excellent article about chimney fires written by the Chimney Safety Institute of America.
Chimney Liner: Please see Flue.
Chimney Lining: This is a round, rectangular, square, or oval protective tubing placed inside the chimney to stop the fumes from escaping through the chimney wall. It can be made from a variety of fire-resistant materials including clay, stainless steel, or pumice.
Chimney Pot: This is the termination point of a masonry, brick, or pumice-built chimney. It is a section of ceramic liner that protrudes above the concrete chimney capping. It can be decoratively shaped or just a plain and straight shape. A chimney cowl can be mounted to it.
Chimney Shaft: A channel created to serve a single heat producing appliance such as a stove or fireplace. A chimney may have several shafts inside it, divided by partition walls.
Chimney Stack: The free-standing section of the chimney that is above the roof line. More liable to wear and tear as it is exposed to the elements on 4 sides.
Chimney: A structural column of masonry, brick, concrete or another material, generally including an inner lining(s), acting as an insulated exhaust for the heat producing appliance.
Condensation: Occurs when the temperature of a moist gas falls below the dew point temperature at which the moisture in the gas turns to droplets.
Creosote: Combustible deposits in a chimney which originate from incomplete fuel combustion. Highly flammable.
Debris: Material caught in the chimney which can obstruct the chimney, restrict the upwards movement of smoke and fumes, and potentially catch on fire and cause a chimney fire. Birds are the biggest offenders and can deposit nesting material in chimneys.
Downdraught: Spelt “downdraft” in North America. Downward moving air which enters the chimney and can cause smoke to puff out from the stove or fireplace.
Draught: Spelt “draft” in North America. The upward movement of warm gases in a chimney. Draught can be increased or decreased as needed.
Electric Chimney Cowl: A motorised chimney cowl driven by electricity that increases draught in a chimney. Used when there is a lack of draught. Please see Chimney Cowl.
External Wall: This is a wall that is exposed to cold air on one side. It can be the outside wall of a building or dwelling. A chimney on an external wall will often be quite cold and may be susceptible to a lack of draught or flow reversal (see below).
Extractor Fan: This is an electric device which pulls air from inside a building and expels it outside.
Fireplace: A fixed area in a chimney breast where a fire is lit from which the resulting fumes will escape up through a chimney.
Flashing: This is protective waterproofing where the chimney meets the roof line. Generally produced from lead, EPDM, or silicone.
Flow Reversal: This is when the draught in a chimney is reversed, with cold air sinking downwards. This can happen when the chimney is not in use. Can be caused by different factors.
Flue: This is the inner liner or tubing that is placed inside a chimney. In Ireland and Great Britain, they are manufactured from clay, stainless-steel or pumice. Please also see Chimney Lining.
Furnace: Please see Boiler and Central Heating.
Heat Producing Appliance: This is the actual unit which is used to burn fuel thus heating the room. It is usually connected to a chimney.
Problem Appliance: It is any appliance that does not work correctly or has an issue with draught. Please see Heat Producing Appliance.
Ridge: This is the highest point of the roof. Also described as the peak or apex of the roof.
Shaft: Please see Chimney Shaft.
Stack: Please see Chimney Stack.
Stove: A closed unit or heat producing appliance, constructed from cast iron or mild steel where fuel is burned and is used to heat the room it is situated or if supplied with a boiler, can heat other rooms through central heating. Please see Central Heating and Boiler.
Tar: This is when soot mixes with moisture, either droplets from condensation or rainwater, and forms a sticky, acidic and smelly, black substance.
Unlined Chimney: This is a chimney that does not have a lining or protective tubing placed inside it. More common in houses more than 40 years old.
Up-Down Problem: This is where there are two chimney’s side-by-side or when two shafts share the one chimney. When a fire is lit in one, smoke rises inside that chimney and is sucked back down the other.