CHIMNEY INFORMATION

Chimney Terminology

A reference glossary of common chimney parts and terms. Use the diagram and definitions below to understand what your sweep is talking about and to make informed decisions about your chimney.

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Anatomy of a Chimney

A masonry chimney is a system of carefully engineered parts. This sectional diagram labels the components a Guild sweep inspects — from the firebox and smoke chamber up through the flue lining, crown, and cap — along with the flashing, anchorage, and footing that keep it safe and weather-tight.

Sectional views of a brick firebox & chimney — on a wood floor (left) and a concrete slab (right). Source: industry standard masonry chimney construction detail.

Glossary of Terms

Common chimney parts and terms, A to Z. Understanding this vocabulary helps you communicate clearly with your sweep.

Ash: The white/grey powdery residue left when combustible materials such as wood and coal is burned.
Ash Dump: An opening located at the bottom of the fireplace, through which ashes can be dumped. Often, there is a door covering the opening than can be open and shut.
Ash Pit: A storage compartment for ashes, located underneath the ash dump. It is usually quite large and should have a access door for cleaning out the ashes periodically.
Baffle: An object or plate installed in an stove or fireplace to change the direction of flue gases often to help burn more effectivley.
Blower: A fan with a motor that is often installed in a fireplace or stove to help distribute the heat being produced.
Carbon Monoxide: An odorless, colorless, tasteless poisonous gas that is a byproduct of incomplete combustion. Carbon monoxide can be fatal if not detected. Please see our Carbon Monoxide Page for more information.
Chimney Chase: The area or structure around metal flue pipes. The chase is usually built with wood or steel studs with an exterior that can include brick/stone veneer or wood siding or stucco
Chimney: One or more passageways, vertical or nearly so for conveying flue gases from the appliance to the outside atmosphere.
Chimney (or Flue) Cap: A protective covering or housing for the top of a chimney. Often, chimney caps have a lid to protect from rain, snow and sleet and a screen mesh of some sort to keep animals out.
Chimney Cleaning (Sweeping): The process of removing soot, creosote, and debris from a chimney. Soot and creosote are by-products of combustion and should be removed regularly from the chimney to help prevent a chimney fire. Chimney cleaning along with an inspection should be preformed as part of an maintence schedule to ensure your chimney operates as efficiently and safely as possible.
Chimney Connector: The pipe connecting a fuel-burning appliance to a chimney. Most commonly made from galanized steel, stove black pipe, or a listed double-wall pipe system.
Chimney Liner: The inner portion of the chimney that contains the products of combustion. It can be made of clay tiles or of metal. The flue chimney liner is one of the most important part of the chimney system. It must be able to contain the products of the combustion process. This means that any holes, cracks or deteriorations must be repaired or replaced to ensure the preformance and safety of the chimney system.
Creosote: Deposits of hydrocarbons that were in the smoke going up the chimney that have condensed into a solid form.
Cricket: (also referred to as a Saddle) A ridge that extends from the back of the chimney to the slope of the roof, with the purpose of shedding water away from the connection between the chimney and the roof.
Crown: A chimney crown (or cap) is the top surface of a chimney designed to shed water away from the flue liner and protect the masonry from water leakage. Often times, the crown should be made of concrete and should have a slope away from the center of the flue stacks.
Damper: A damper is a device for controlling the flow of air or smoke in a chimney or woodstove. In its most common form, plate located in the fireplace or stove pipe with a control handle. For some stove there is an additional air control damper located on the exterior of the stove.
Draft: The rising gas creates a pressure difference called draft, which draws combustion air into the appliance and expels the exhaust gas outside through the chimney.
Dryer Vent Cleaning: Lint that normally occurs in a clothes dryer can build up over time. Build-up of lint causes the dryer to take more time in drying the standard load of clothes and becomes a fire hazard. Dryer vent cleaning is a service in which the built up lint is removed from the dryer venting systems.
Firebox: Chamber of a fireplace or stove where the fire actually burns.
Firebrick: Brick composed of clay and silica and designed to withstand high temperatures such as those found in a firebox.
Fireplace Inserts: Wood, coal, pellet, or gas heating appliances that fit inside an existing fireplace.
Flashing: Sheet metal or other materials used in waterproofing roof valleys or the angle between a chimney and a roof.
Flue: The passage in a chimney for conveying flue gases to the outside atmosphere.
Flue Liner: Special liner required by codes and standards to cover the inner surface of the flue. The liner serves as a buffer between flue gases and chimney walls and is designed to contain the products of combustion.
Hearth: Floor area within the firebox of a fireplace or a fireplace stove.
Hearth Extension: The a structure, usually consisting of stone, masonry or tile that protrudes in the living area of the house.
Masonry Chimney: A field-constructed chimney of bricks, stones or reinforced Portland cement concrete, lined with suitable chimney flue liners built in accordance with applicable building code requirements.
Masonry Fireplace: A hearth and firebox of solid masonry units such as bricks, stones, listed masonry units, or reinforced concrete, provided with a suitable chimney.
Multi-flue Chimney: A single chimney containing more than one flue.
Pellets: Small balls or blocks made of wood sawdust with no additives.
Parging: A thin coat of mortar applied to the inside of a masonry chimney or to the walls of a smoke chamber designed to reduce the resistance of flow in the chimney system.
Pyrolysis: Chemical alteration of wood, coal, or other combustible materials as a result of the application of heat.
Smoke Chamber: Chamber in a fireplace directly above the smoke shelf and extending to the base of the flue.
Smoke Shelf: The area at the bottom of the smoke chamber created as the back wall of the firebox arches forward. The shelf is located at the intersection of the smoke chamber and the firebox. A damper is normally located on the forward side of the smoke shelf.
Stainless Steel Liners: Stainless steel pipe, either rigid or flexible, made for relining flues of masonry chimneys when the original clay liner has cracked or broken. May also be used to create a lining in a masonry chimney that was made without a clay liner.
Soot: Soft, black, or brown, velvety carbon particle deposits inside appliances, chimneys or connectors, originating in oxygen-poor flames.
Stack Effect: The tendency for warmer air to rise within a structure, creating lower pressure in the lower areas of the building.
Thermal Expansion: Alteration to temperature inside a chimney or duct system that causes the metal surfaces to expand.
Thimble: Fixed or removable ring, tube, or lining usually located in the hole where the chimney connector passes through a wall and enters a chimney or vent.
Throat: Opening above a fireplace firebox through which flue gases pass from the firebox to the flue. The fireplace damper frame assembly is usually located at the throat of a fireplace.
Vent: A continuous passage from the flue collar to the draft hood. Flue gas temperatures at the outlet do not exceed 600 degrees.
Video Scan: Incorporating a closed circuit video camera and monitor, for inspecting the interior of flues and other inaccessible areas. This provides a very detailed part of the inspection process.
Woodstoves: Enclosed appliances, most commonly constructed of steel or cast-iron, used for burning wood for the purpose of heating an indoor space.