Chimneys, Flues and Venting Inspection Glossary of Terms and Conditions

Abandoned connections - Openings in a chimney or flue where an appliance was previously connected but has since been removed. These openings should be properly sealed to prevent exhaust gases, debris, or moisture from entering the building.

A vent - A general term sometimes used for a venting system approved for a particular appliance or fuel. The exact classification and permitted use depend on the applicable venting standard.

Air vent - An opening or device that allows air to enter or escape from a heating or venting system. In a chimney or boiler system, its purpose depends on the particular installation.

B vent - A factory-made, double-wall vent commonly used to carry exhaust gases from certain gas-burning appliances. It relies on natural draft and must be installed with the required clearances from combustible materials.

BW vents - A type of listed gas vent intended for specific wall-furnace installations. Its use is restricted to compatible appliances and the manufacturer's installation requirements.

Cap / Caps - A protective covering installed at the top of a chimney or vent. It helps keep out rain, snow, animals, and debris. Some caps also help reduce downdrafts or prevent sparks from escaping.

Chimney - A vertical structure or passage that carries combustion gases from a fireplace, stove, furnace, or other appliance to the outdoors.

Chimney extender - A component added to the top of a chimney to increase its height, sometimes to improve draft or bring the chimney termination into compliance with clearance requirements.

Chimney height above roof - The vertical distance between the roof surface and the top of the chimney. Adequate height is necessary for proper draft and to reduce interference from nearby roof surfaces or obstructions.

Combustible clearance / Combustible clearances - The minimum required separation between a chimney, vent, connector, or other heat-producing component and nearby combustible materials such as wood framing, insulation, or siding.

Combustible clearance requirements - The required distances between hot surfaces and combustible building materials. Requirements vary according to the appliance, venting system, listing, and installation instructions.

Condensation - The formation of liquid water when water vapour in exhaust gases cools below its dew point. Condensation inside a chimney or vent can damage masonry, corrode metal, and contribute to deterioration.

Corbelling - A masonry construction technique in which successive courses of brick or stone project outward beyond the courses below. It is sometimes used to widen or support a chimney structure.

Creosote - A flammable deposit produced by incomplete combustion of wood. It can accumulate inside chimneys and flues, creating a serious chimney-fire hazard.

Draft - The flow of air and combustion gases through a chimney or vent, generally caused by differences in temperature and pressure between the appliance and outdoors. Adequate draft helps remove combustion products.

Draft inducer - A powered fan used to establish or assist the movement of combustion gases through an appliance's heat exchanger and venting system.

Deteriorated masonry - Brick, stone, or other masonry that has weakened, cracked, separated, or broken down due to moisture, weathering, heat, or other causes.

Deteriorated mortar - Mortar between masonry units that has cracked, crumbled, loosened, or eroded. Deteriorated mortar can allow moisture penetration and reduce the stability of a chimney.

Efflorescence - A white, powdery deposit of mineral salts on masonry surfaces, caused when moisture carries dissolved salts to the surface and evaporates.

Factory-built chimneys - Manufactured chimney systems, generally consisting of insulated metal sections and approved fittings. They must be installed according to their listing and manufacturer's instructions.

Fire stopping - Materials or construction details installed to restrict the movement of fire and smoke through concealed spaces, such as wall cavities, floor assemblies, and openings around chimneys or vents.

Flue - A passage through which combustion gases travel from an appliance or fireplace to the outdoors. A chimney may contain one or more separate flues.

Flue liner - The inner lining of a chimney flue, designed to contain combustion gases and protect surrounding masonry from heat, corrosive gases, and condensation. Liners may be made of clay tile, metal, or other approved materials.

Foundation - The portion of a chimney or other structure that transfers its weight to the supporting soil or building structure.

Height - The overall vertical dimension of a chimney or vent. Height affects draft, performance, and compliance with installation requirements.

Leaning - A condition in which a chimney or other structure is no longer vertical. It may indicate foundation movement, structural deterioration, or inadequate support.

L vent - A listed venting system designed for certain oil-burning appliances and other specifically approved applications. Its construction and clearances differ from those of B vents.

Multiple appliances - Two or more fuel-burning appliances connected to a shared chimney or venting system. Such arrangements are permitted only when the appliances and venting system are approved for common venting and properly sized.

Offset - A change in the direction of a chimney or vent, usually involving angled sections that allow it to pass around an obstruction. Offsets can affect draft and may require additional support or cleaning access.

Pitting - Small holes or cavities caused by corrosion on metal chimney or vent components. Pitting can weaken the material and eventually lead to perforation.

Settling - Downward movement of a chimney or its foundation. Uneven settling can cause cracks, separation from the building, and changes in alignment.

Spalling - The flaking, chipping, or breaking away of masonry surfaces, often caused by moisture penetration, freeze-thaw cycles, or heat damage.

Support - Structural components or brackets that hold a chimney or vent in position and transfer its weight or other loads safely to the building structure.

Total chimney height - The overall vertical height of the chimney, generally measured from its base or appliance connection to its termination. It can affect draft and the suitability of the chimney for a particular appliance.

Vent connectors - Pipes or fittings that connect an appliance's exhaust outlet to a chimney or vent. They must be properly sized, supported, assembled, and installed with required clearances.

Vents - Passages or manufactured systems that carry combustion gases from appliances to the outdoors. Different vent types are designed for particular fuels, appliances, and operating temperatures.

Walls - The masonry or other structural surfaces forming the sides of a chimney. They must remain stable, adequately supported, and sufficiently intact to contain the flue system.