With the help of Valor® , The Hearth Shop and Kastle Fireplace we at the Fireplace Stop have compiled a glossary of words or phrases frequently associated with the fireplace industry to help in providing you with more information when researching, planning, designing and accessorizing your fireplace. If you do not see a term listed, please contact one of our experts the Fireplace Stop and we’ll be happy to help you.

ANSI — American National Standards Institute. The organization responsible for coordinating the federal national standards system, consisting of 900 companies and 200 trade, technical, professional, labor and consumer organizations.

APPLIANCE — A solid or fossil fuel burning stove, fireplace, furnace, boiler, water heater, heater or cook stove.

B VENT — See Type B Gas Vent.

BLOWER — An electric, motor driven fan used to circulate air at an increased pace and velocity through the fireplace convection air chamber.

BTU OR BRITISH THERMAL UNIT — A unit for measuring energy, equal to the amount of energy needed to increase the temperature of 1 pound of water by 1 degree Fahrenheit.

CAST IRON — A material used in many fireplaces. Iron is heated to a liquid form and poured into molds, usually having decorative features.

CERTIFIED — Equipment or material identified as having undergone approved inspection and compliance manufacturing and performance procedures.

CHASE — A structure built around, and enclosing, portions of chimney exterior to the house.

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.

CIRCULATING FIREPLACE — A fireplace with multiple-wall construction around the fire chamber which permits air to circulate between the walls, become heated, and enter the house directly.

CIRCULATING STOVE — Also see circulating fireplace. A stove with an outer jacket (usually sheet metal) beyond the main structure, with openings at or near the bottom and top so that air can circulate between the stove body and its jacket. For purposes of determining safe clearances, a circulating stove must be fully jacketed on all four sides, including at the access doors and on the top.

CLEARANCES — Minimum distance, composed only of an air space, which must be maintained between a heat source such as a fireplace or vent and combustible surfaces. Distance required by building and fire codes between stove, fireplace, or chimney and combustible materials such as wood furniture or carpets. Clearances must be obeyed even if the combustible materials covered by noncombustible plaster or other masonry materials.

CO-AXIAL DIRECT VENT — A Direct Vent system consisting of a length of sealed, exhaust pipe inside a same length of a larger diameter combustion air pipe. Basically a pipe within another pipe – center is exhaust and outer donut area is fresh air.

CO-LINEAR DIRECT VENT — A Direct Vent system consisting of two separate pipes of the same diameter. One pipe for exhaust and the other for combustion air.

COMBUSTIBLE MATERIAL — 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.

CONDENSATION — The liquid byproduct (water) of gas combustion, usually most visible at fireplace start up.

CONVECTION HEATING — The natural movement of air as it heats up and expands. This creates a natural flow of air as the warmer air moves upward and is replaced by cooler air.

CSA — Canadian Standards Association International test products for compliance to national and international standards, and issue certification marks for qualified products. Certification marks tell potential customers and users that a product has been evaluated by a formal process-involving examination, testing and follow-up inspection – and that it complies with applicable standards for safety and performance.

DAMPER — a metal device inside the fireplace chimney used to reduce or close the opening between the firebox and flue; stops cold chimney drafts

DECORATIVE GAS APPLIANCE IN A VENTED FIREPLACE — A self-contained, freestanding fuel/gas-burning appliance designed for installation only in a vented fireplace and whose primary function lies in the aesthetic effects of the flame. Gas hearth appliances which are listed to ANSI Standard Z21.60 include gas log sets.

DIRECT VENT APPLIANCES — Direct vent hearth appliances draw combustion air from outdoors and exhaust its combustion products to the outdoors eliminating the need for a standard chimney system. A glass panel in direct vent units is critical to keeping the combustion system sealed from the home, maintaining high efficiency and indoor air quality.

DIRECT VENT — Method of venting appliance whereby all air for combustion is derived directly from the outside atmosphere and all flue gases are discharged directly to the outside atmosphere. Exhaust system for gas fireplaces that is gravity induced. No chimney is required.

DOWNDRAFT — a strong, downward current of air

EFFICIENCY — The percentage of heat that goes into the room instead of up the chimney.

ENERGY EFFICIENCY — The percentage of the total energy content of the fuel consumed that becomes useful heat in the house.

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.

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.

FAN — See Blower

FIREBOX — The inner most compartment of a fireplace designed to support the combustion of fuel.

FIREPLACE — An enclosure, open in the front, used to burn fuel. Solid fuel fireplaces may contain, and vent, gas fireplace inserts. Gas fireplaces are metal appliances open in the front and containing artificial log sets.

FLEXIBLE CHIMNEY LINER — Listed, factory-built, double walled, continuous, flexible metal pipe for venting gas appliances. Used strictly within masonry or factory built chimneys to vent flue gases vertically to the outdoors. Flexible Chimney Liner is also used on Direct Vent or Co-linear Vent Insert appliances to supply combustion air from outdoors.

FLUE — The passageway in a chimney for conveying flue gases to the outside atmosphere.

FLUE GASES — The gases in an operating venting system, consisting of combustion products plus whatever air is mixed with them.

FREESTANDING GAS STOVE — An appliance with gas burning log set that has the appearance of a solid fuel appliance that is placed away from walls in a dwelling.

FURNACE — A central heating appliance that supplies hot air, through ducts, to the house.

GAS FIREPLACE INSERT — A gas appliance designed to be installed within an existing masonry fireplace opening or a metal factory-built firebox. It offers superior efficiency.

GAS VENT — A factory made, listed venting system designed to remove flue gases to the outside atmosphere. Please also see Direct Vent, Type B vent or Flexible Chimney Liner.

GRAVITY VENT — Type of venting that uses the natural draft of a column of warm gases rising due to the pressure of surrounding cooler air.

HEARTH — a.Traditionally refers to the floor of a fireplace on which a blaze is built. Now also used to refer to all the devices and equipment used in connection with the fireplace and stove industry.

HEARTH — b.The surface under and/or in front of your stove or fireplace, often made of brick, or tile.

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 temperatures inside the house. Used for determining necessary heat output from the heating appliance.

HEAT OUTPUT — The amount of useable heat produced by a heating appliance; expressed in BTU’s per hour.

Hood — Also known as a ‘canopy’. Somewhat self-explanatory. Some cast iron fireplaces had a canopy above the firebox aperture, initially to catch any escaping smoke and direct it up the Chimney, thus helping prevent back drafts. Nowadays they are purely decorative and some fireplaces have them included as standard. Hoods can also be purchased as separate items and fixed to a unit if required.

Hopper — A container for a fuel source such as wood pellets or coal that is attached to an appliance so that the fuel is fed to the burner.

H.P.B.A. — Hearth, Patio & Barbecue Association (HPBA) is an international not-for-profit trade association first established in 1980 to represent and promote the interests of the hearth products industry in North America. In 2002, the Hearth Products Association (HPA) merged with the Barbecue Industry Association (BIA) to form HPBA. The association includes manufacturers, retailers, distributors, manufacturers’ representatives, service and installation firms, and other companies and individuals – all having business interests in and related to the hearth, patio, and barbecue products industries.

H.P.B.A.C. — The Hearth, Patio and Barbecue Association of Canada (HPBAC) is a trade association, dedicated to serving the needs of our members, established for the purpose of: providing a voice for the industry, promoting and protecting the interests of those engaged in the hearth, patio and barbecue industries, coordinating and integrating the needs of industry dealers, distributors, manufacturers and suppliers, providing educational and networking opportunities to all our members on both national and regional levels, promoting consumer awareness of the benefits associated with our products.

INSERT — See Gas Fireplace Insert.

LIQUEFIED PETROLEUM GAS (LPG) — Colorless, odorless, and non-toxic gas separated from wet natural gas, light crude oil, and oil refinery gases. Composed predominantly of following hydrocarbons or mixtures thereof: propane, propylene, normal butane or isobutane and butylenes. Please also see Liquid Propane.

LIQUID PROPANE — Liquefied Petroleum Gas, available in cylinders, for home use. Please also see Liquefied Petroleum Gas.

LISTED — Included in a list published by a recognized testing laboratory or inspection agency, indicating that the equipment meets nationally recognized safety standards.

MANIFOLD PRESSURE — Gas pressure between the combination valve and the burner orifice.

MANOMETER — Instrument used for measuring the pressure of gases.

MANTEL — Shelf over and above the fireplace opening. Stone, brick or wood may be used.

MANUFACTURERS INSTALLATION INSTRUCTIONS — Instructions and recommendations for proper assembly, adjustment, and installation of listed equipment.

MASONRY CHIMNEY — Chimney constructed on site of masonry and fire clay materials; construction requirements specified by code. Also refers to existing masonry chimneys of various constructions.

METHANE — Main constituent of natural gas. Chemical formula CH4.

MILLIVOLT (MV) — Unit of electromotive force equal to one one-thousandth of a volt.

MOBILE HOME APPROVED — Solid fuel appliance specifically designed to meet HUD standards for installation into mobile homes. Includes outside combustion air, floor mountings, substantially reduced clearances, and designated venting systems.

MODULATING CONTROL — The ability to control the fuel input to the gas fire automatically – similar to the cruise control on an automobile. Available with Valor’s standard ValorStat Control System.

NATIONAL FUEL GAS CODE (ANSI Z23.1, NFPA 54) — A standard for the installation of gas appliances, piping and venting.

NATURAL DRAFT APPLIANCES — Natural draft hearth appliances take in combustion air from the home and vent products of combustion outside the home. Also referred to as: Chimney Vented, B Vented or Gravity Vented Appliances.

NATURAL GAS — Clean-burning fossil fuel available in vast quantities throughout North America and delivered to homes via an extensive pipeline network. Colorless, highly flammable gas found in porous geologic formations beneath the earths surface. Consists mainly of methane.

ORIFICE — The opening in a cap, spud, or other device whereby the flow of gas is limited and or controlled and through which the gas is discharged to either a pilot burner or main burner.

PIEZO IGNITOR — A device which delivers an igniting spark by means of pressure on a crystal.

PILOT — A small flame used to ignite the gas at the main burner.

PRESSURE REGULATOR — A device for controlling and maintaining a uniform outlet gas pressure. Service regulators reduce high street pressure of natural gas or reduce LPG storage tank pressure. Appliance regulators, usually part of the combination valve, reduce, adjust and maintain constant pressure to be used in an appliance.

PRESSURE TEST — Method of checking for leaks in the gas supply line prior to installation of appliances.

PRIMARY AIR — Combustion air directed to the firebox where the fuel is located; supports all stages of combustion.

PROPANE — A colorless, odorless, nontoxic LPG containing more heat value than natural gas.

PSI — Pounds of pressure per square inch.

RADIANT HEAT — Heat that moves out in waves from a central point and heats objects in its path. The invisible and harmless radiation emitted by a hot object. This radiation is converted into heat when it is absorbed.


SAFETY SHUTOFF — A device, powered by a thermocouple, designed to shut off the gas supply to the pilot and or main burner if the source of ignition fails.

SECONDARY AIR — Combustion air directed downstream of the primary combustion zone (but still in the appliance) to support the combustion of remaining combustible gases; does not directly influence the rate of primary combustion.

SEDIMENT TRAP — In gas piping, a tee device to intercept or hold solid foreign particles to prevent them from blocking valves or orifices. Not part of an appliance, must be installed as close to appliance inlet as possible. Also referred to as a Drip Leg.

SILICONE SEALANT — Process of sealing cracks with a high temperature silicone sealant.

SOLID FUEL — Wood, coal, and other similar organic materials in various forms (e.g. chunk wood, pressed logs, wood pellets, wood chips, paper, processed coal, coke, peat, charcoal).

STEADY STATE EFFICIENCY — The ratio of the heat or BTU output vs. the heat or BTU input under steady conditions.

TEMPERATURE DIFFERENTIAL — The difference in temperature between two areas, such as inside and outside the chimney or house. (Example, if it is 50 degrees F. outside the house and 70 degrees F. inside the house the temperature differential is 20 degrees F.)

THERM — 100,000 British Thermal Units (BTUs)

THERMAL EFFICIENCY — The percentage of heat, which is released in the fire, that gets through the appliance to become useful heat in the house.

THERMOCOUPLE — A device consisting of two pieces of dissimilar metals joined together at one end (hot junction). When the hot junction is heated, the thermocouple produces DC voltage across the other end. Used to power thermoelectric gas valves.

THERMOSTAT — An automatic device for regulating the temperature in a building by controlling the heating or cooling source. Acts strictly as an on/off switch – does not modulate the heating or cooling source.

TYPE B GAS VENT — Listed, factory-built, double wall metal pipe for venting gas appliances with draft hoods and other appliances listed for use with Type B Gas Vent.

U.L. LISTED — Underwriters Laboratories, Inc. 333 Pfingsten Road, Northbrook IL, 60062. An independent not-for-profit organization testing for public safety.

UNVENTED ROOM HEATER — category of unvented, self-contained, free standing, non recessed (except as noted) fuel gas burning appliance for furnishing warm air by gravity or fan without duct connection. Gas hearth appliances listed to ANSI Standard Z21.11.2 include Gas Fireplaces and Fireplace Inserts.

UNVENTED OR VENT-FREE APPLIANCES — Unvented or vent-free refers to the kind of hearth appliances that draws its combustion air from inside the home and is designed to burn so efficiently that it eliminates the need for venting.

VALORSTAT — A wireless handheld remote control system which allows the user complete control of the fire from anywhere in the room. Standard equipment on most Valor models – controls the comfort, convenience and aesthetics you want from your Valor gas fireplace. See Modulating Control.

VENTED DECORATIVE APPLIANCES — A vented appliance whose only function lies in the aesthetic effect of the flames. Gas hearth appliances tested to ANSI Standard Z.21.50 include gas fireplaces, fireplace inserts, and freestanding appliances.

VENT-FREE — Gas appliances that have no flue.

VENT-FREE APPLIANCES OR UNVENTED — Vent-free or unvented refers to the kind of hearth appliances that draw its combustion air from inside the home and are designed to burn so efficiently as to eliminate the need for venting.

VENTING SYSTEM — A continuous open passageway from the flue collar or draft hood of the appliance to the outside atmosphere for the purpose of removing flue gases.

WATER COLUMN (WC) — Measurement in inches of pressure of gas. 28 inches wc equals one psi.

ZERO CLEARANCE FIREPLACE — A factory-built metal fireplace with multi-layer construction providing enough insulation and/or air cooling so that the base, back, and in some cases sides, can safely be placed in direct contact (zero clearance) with combustible floors and walls.

Additional Glossary terms can be found at and