Glossary of Industry Terms

Air Inlet – The designed port(s) of entry for combustion air in a controlled combustion, wood burning appliance.

Air Supply – Broadly, the air that is supplied to the firebox of the woodburning appliance.

Ash – Noncombustible solid byproduct of solid fuel combustion.

Baffle – An obstructing device or partition in a wood burning appliance, used to direct the flow of gases and heat.

BTU or British Thermal Unit – A measure of heat energy; the amount of heat required to raise the temperature of one pound of water one-degree Fahrenheit at sea level.

Burn Rate – Combustion rate, usually expressed in pounds of fuel consumed per hour.

Cap – Also called termination cap.  Covering for factory-built chimney that minimizes the effect of wind, and prevents entry of rain, snow, and debris into the chase.

Carbon Dioxide (CO2) – Colorless, odorless noncombustible gas produced by the complete combustion of carbonaceous fuel; is nontoxic.

Carbon Monoxide (CO) –  Colorless, odorless, combustible, and toxic gas produced by the incomplete combustion of carbonaceous fuel.

Catalytic Combustor – Device designed to increase combustion efficiency by lowering flue gas ignition temperatures.  Consists of substrate, washcoat, catalysts, and canning system.

Chase – A structure built around, and enclosing, portions of the chimney and in some cases, housing the appliance.

Chimney – A portion of the venting system, through which flue gases are vented to the outdoors and by which penetrated combustible surfaces are protected; a primarily vertical shaft enclosing at least one flue, the design of which results in a natural draft.

Clearances – Minimum distance which must be maintained between a heat source such as an appliance or vent and combustibles surfaces.

Combustible Material/Combustibles – Material made of or surfaced with wood, compressed paper, plant fibers, or other material that will ignite and burn, as applied to materials adjacent to or in contact with heat-producing appliances, chimney connectors, steam and hot water pipes and warm air ducts.  Such material shall be considered as combustible even though flame-proofed, fire retardant treated, or plastered.

Combustion – The process of burning, or oxidation accompanied by heat.  When sufficiently rapid, also accompanied by light.  Rapid oxidation of fuel gases accompanied by the production of heat, or heat and light.  Requires proper amounts of fuel, oxygen, and heat.

Combustion Ratio – Required amount of air that must mix with 1 cubic foot of gas to have complete combustion.

Condensate – The liquid that separates from a gas due to a reduction in temperature.

Damper – Movable plate that directs the flow of gases and air in a solid fuel appliance or chimney connector.  In fireplaces, a pivoted metal plate, set just above the firebox, primarily used to close off the chimney when not in use. 

Drip Leg – In gas piping, a tee device used to collect condensate from gases.  Installed so that they can be serviced to remove condensate.

Drywall – A manufactured panel made out of gypsum plaster and encased in a thin cardboard or other material.

Elbow – The portion of the connector or chimney that turns or offsets the direction of the chimney.

Electronic Sniffer – A device that emits a loud, piercing noise in the presence of very small amounts of certain gases.  Used in gas supply line and appliance leak detection.

Factory-Built Chimney – A chimney composed entirely of listed manufactured components, designed to be assembled as an entire system in accordance with the terms of the listing.

Factory-Built Fireplace – Prefabricated metal fire chamber and its chimney, commonly called “zero clearance.” Consists of listed manufactured components that are assembled in accordance with the terms of the listing to form the completed fireplace.

Fire Resistance Rating – The time a material will withstand, without igniting, flame and heat as specified by code and specific test conditions.

Firebox – That portion of the solid fuel appliance where the fuel is located and where primary combustion occurs.

Firebrick – Heat resistant brick used in fireboxes; withstands very high temperatures.

Fireplace – An enclosure, open in the front, for burning fuel.  Solid fuel fireplaces may contain and vent gas log sets or fireplace inserts.  Gas fireplaces are metal appliances open in the front and containing artificial log sets.

Fireplace Inserts – Solid fuel appliance designed to be installed partially or fully in the fire chamber of an existing masonry fireplace, and that vents into the fireplace chimney by means of full relining or appliance to flue methods.

Firestop – A noncombustible barrier, often metal, placed to span the air space between the outer walls of chimneys and surrounding combustibles; serves to resist the spread of fire between floors of a structure.

Flame Impingement -The “striking” of flame against an object, such as a log.

Flashing – A metal device that covers a factory-built chimney roof penetration and helps stabilize the chimney.

Floor Protection – Noncombustible material of specified size, thickness, material and conductivity placed under a solid fuel appliance; required to extend beyond the four sides of the appliance. Protects combustible floor surfaces and framing.

Flue – The passageway in a chimney for conveying flue gases to the outside atmosphere.

Flue Gases – All combustible and noncombustible gases (plus excess air) that exit the solid fuel appliance.

Flue Liner – The portion of the chimney that contains the flue gases.  It is separated from the interior of the masonry chimney wall by an air space.

Furnace – A central heating appliance that supplies hot air, through ducts, to the house.

Gable – The end, upper, triangular area of a home, beneath the roof.

Gas Logs – An open flame type appliance consisting of a burner and metal pan or base supporting simulated logs.  May also include various ember media.

Gas Vent – A factory-made, listed venting system designed to remove flue gases to the outside.

Gravity Ducting – Movement of heated air by non-mechanical means.  Rising warm air travels to heat register higher than heat source and flows back as it cools and falls.

Header – A beam placed horizontal above doors, windows or other openings to carry the weight of structural loads.

Hearth – The floor of the firebox, most commonly used in reference to fireplaces.  The foundation upon which fires for aesthetic and heating purposes are built.

Hearth Extension – Noncombustible floor protection in front of and to the sides of a fireplace hearth.

Heat Loss Calculation – Calculation to determine house BTU loss; factors include conduction through construction materials, air infiltration losses and the difference between actual or projected outside temperatures and desired temperature inside the house.  Used for determining necessary heat output from the heating appliance.

Heat Output – The amount of usable heat produced by a heating appliance; expressed in BTU.

Heat Value – Amount of heat potential of one cubic foot of gas when burned.  Also known as caloric value.

Hip Roof – A roof that rises by inclined planes from all four sides of a building.

Hot Junction – Joined, heated end of thermocouple/thermopile.

Hybrid Woodstove – A solid fuel appliance with dedicated air passages for the combustor, but also with separated dedicated air passages for secondary air combustion.  Designated by EPA as a catalytic woodstove.

Ignition Temperature – The lowest temperature at which combustion occurs.

Intermittent Pilot Ignition – Means of lighting the pilot or main burner without the use of a standing pilot, by electronic spark or hot surface ignition.  Also know as electronic ignition device.

Incomplete Combustion – Improper air/fuel mixture or inadequate temperatures resulting in less than complete burning of fuel.

Leakage Testing – Procedure to ensure that there is no uncontrolled flow of fuel gas in the piping system and/or the appliance.

Liquified Petroleum Gas (LP) – Colorless, odorless, and non-toxic gas usually stored in a tank.

Main Gas Burner – Device for the final conveyance of gas or a mixture of gas and air to the combustion zone. Consists of burner orifice, air shutter, mixer, and burner head.

Manometer – Instrument used for measuring the pressure of gases.

Masonry Chimney – A field-constructed chimney of solid masonry units, including brick, stone or other listed masonry material.

Multimeter – A device consisting of one or more meters used to measure two or more electrical quantities in an electrical circuit, such as voltage, resistance, and current.

Natural Gas – Colorless, highly flammable gas found in porous geologic formations beneath the earth’s surface.  Consists mainly of methane.

Noncombustible – A material that, when used properly, will not ignite, burn, support combustion, or release flammable vapors when subjected to heat.

Odorant – Material added to natural gas or propane in small amounts to create a detectable distinct odor.

Orifice – The opening in a cap or other device whereby the flow of gas is limited and/or controlled.  Gas is discharged through this to either a pilot burner or main burner.

Oven Dry Wood – Wood dried at 217 degrees F to a constant weight.  Defined as having “aero moisture content”.

Piezo Starter – A device that delivers an igniting spark by means of pressure on a crystal.

Pilot – A small flame used to ignite the gas at the main burner.  May be standing (constantly burning) or intermittent (on demand and during heat).

Pilot Safety Shutoff System – A component of the pilot or the gas control valve that allows or shuts off gas flow on the basis of the presence or absence of flame.  Also known as millivolt system.

Pressure Regulator – A device for controlling and maintaining a uniform outlet gas pressure.  Service regulators reduce high street pressure of natural gas or reduce propane storage tank pressure.

Pressure Drop Test – Method of checking for leaks in the gas supply line prior to installation of appliances.

Propane – Liquid petroleum, LP, LPG; colorless, odorless, non-toxic, containing more heat value than natural gas.

PSI – Pounds of pressure per square inch.

Safety Shutoff – A system, usually powered by a thermocouple/thermopile or by an electronic control module, designed to shut off the gas supply to the pilot and/or main burner if the pilot or main burner flame is lost unexpectedly.

Sediment Trap – In gas piping, a tee device to intercept or hold solid particles to prevent them from blocking valves or orifices.

Solid Fuel – Wood, coal, and other similar organic materials. (pressed logs, wood pellets, wood chips, paper, processed coal, coke, peat, charcoal, corncobs)

Soot – Soft, black or brown, velvety deposit of carbon particles inside appliances, chimneys, and connectors.

Spark Arrester – A noncombustible screen installed between installed between the top of the chimney and the underside of the chimney cap; prevents the escape of sparks and burning materials from the chimney.

Storm Collar – Metal plate or collar fastened and sealed with high temp. sealant around the chimney just above the roof flashing. Prevents water from entering the space between the chimney and the roof flashing.

Termination – Components at the very top of the chimney.

Type B Gas Vent – (B vent) Factory-built, double wall metal pipe for venting appliances with draft hoods.

Unvented Room Heater – Category of unvented, self-contained, free standing gas burning appliance for furnishing warm air by gravity or fan without duct connection, includes gas fireplaces and fireplace inserts.

Venting Systems – A continuous open passageway from the flue collar or draft hood of the appliance to the outside for the purpose of removing flue gases.

Water Column (WC) – Measurement in inches of pressure of gas.  28 inches WC equals one psi.