Guide to Fireplace Terminology. Air Supreme Filter Cleans room air when blower is operating Blue Flame Rectification Safety shut-off device. Proves the flame and the control center maintains the gas flow. BTU Unit to measure heat. Stand for "British Thermal Unit" Burner Device for the final conveyance of gas or a mixture of gas and air to the combustion zone. Burner Ports Holes in the burner Carbon Dioxide A gas which is product of combustion resulting when carbon units with sufficient oxygen to produce complete combustion. Carbon dioxide is a component of many natural gases. Carbon Monoxide A poisonous, combustible gas formed by incomplete combustion of carbon or reduction of carbon dioxide. Catalytic Combustor A device used on some wood burning stoves to reduce the temperature at which smoke is ignited. CFM A measure unit for air flow. Stand for Cubic Feet per Minute. Indication for the strength of the fun. Chimney One or more passageways, vertical or nearly so, for conveying flue gases or vent gases to the outside atmosphere. See also: gas vent, vent, and venting system. Circulation Fun A Fun installed in a Fireplace that help to heat a home by force the Hot air to circulate around. Clearance The distance required by building and fire codes between stove, smoke pipe or chimney and combustible materials such as wood furniture or carpets. Clearances must be obeyed even if the combustible materials, such as wood furniture or carpets, are protected by noncombustible plaster or other masonry materials. Creosote A very flammable by-product of combustion that can buildup within the smoke pipe and chimney and then ignite, causing "chimney-fire". Damper A device used to reduce or close the opening between the firebox and flue. Decorative Front Fixed mesh screen front placed in front of glass panel for aesthetics and safety. Installed on all direct vent fireplaces. Decorative Gas Appliance for Installation in a Vented Fireplace A self-contained, free-standing fuel-gas burning appliance designed for installation only in a vented fireplace and whose primary function lies in the aesthetic effect of the flame. Direct Spark Ignition A type of electronic pilot ignition. It ignites the gas directly at the burner from a spark. Direct Vent Wall Furnace A system consisting of an appliance, combustion air and flue gas connections between the appliance and the outside atmosphere, and a vent cap supplied by the manufacturer and constructed so that all air for combustion is obtained from the outside atmosphere and all flue gases are discharged to the outside air. Draft Hood/Draft Diverter A device built into an appliance or made a part of the flue or vent connector from an appliance, which is designed to Provide for the ready escape of the product of combustion (flue gas) from the combustion chamber in the event of no draft, back draft, of stoppage beyond the draft hood; Prevent a back draft from entering the combustion chamber of the appliance; Neutralize the effects of stack action of the chimney or gas vent upon the operation of the appliance. Electronic Ignition System A device to light the burner or pilot that requires electrical current but not a match. Emissions By-products of combustion vented out of the home. Factory-Built Chimney A chimney composed of listed factory-built components (usually stainless steel and galvanized steel) that is easy to assemble to form the completed chimney. They conform to safety and building codes. They are air cooled or insulated. Designed to remove combustion by-products. Firebacks Protect fireplace masonry and mortar, shielding them from extreme heat of the flames. Cast-iron firebacks store heat from the fire and radiate it into the room after the fire has died down. Firebacks work just as well in a modern gas fireplace as they do in a traditional wood burning one. Fireplace Inserts A type of decorative appliance consisting of an open-flame radiant-type appliance mounted in a decorative metal panel to cover the fireplace or mantel opening and having provisions for venting into the fireplace chimney. Firestops Devices of noncombustible material that seal any openings separating floors so that smoke or fire can not penetrate from one level to another. Flue Vent or chimney for a combustion device. Freestanding Stoves A heating appliance normally on legs or a pedestal that occupies an area roughly equal to that of an easy chair. Flue Collar Ring on appliance designed for the attachment of the draft hood, vent connector or venting system, that determines the size of the vent. Gas Cock Assembly Also called valve control, a part of the combination valve that is a multi-positioned and tapered valve. When in the "on" position, it allows for the flow of gas to the burner. In the "off" position, it shuts off the gas supply to the appliance. Gas Log An open flame type appliance consisting of a metal frame or base supporting simulated logs. Glass Doors Close off the opening of the hearth so heat from the central heating system does not escape up the chimney when the fireplace is not being used. Glass Panel Provides safety and energy efficiency to gas fireplaces. Grate An iron frame used to hold burning fuel in a fireplace. Hearth Traditionally refers to the floor of a fireplace on which a blaze is built. Today it is also used to refer to all the devices and equipment used in connection with the fireplace and stove industry. Heat Shield A non-combustible protector used around appliances, smoke pipe or chimney. Gas Vent A factory-made vent for venting listed gas appliances with draft hoods and other gas appliances. Special Vents: vent system designed for flue gases that do not rise easily. They are composed of two types: sealed combustion vents and power exhauster vents. Type B gas vent: double-walled vent with a relatively low permissible temperature for venting gas in gas appliances only. Hopper A container attached to an appliance in which fuel, either coal, nuggets or wood pellets, is stored and from which the fuel is fed to the burner. Hot Surface Igniter A type of electronic ignition system. Ignition Systems Devices that ignite the pilot burner and/or the main burner assembly. Junction Box Wire to 110 VAC for optional remote control or blower. Wire 110 for HSI units. Limit Switch Devices constructed of bimetallic material that react to excessive temperature in an appliance and shut down the gas flow to it. They break or stop the flow of electricity and prevent the operation of the gas appliance. Liquefied Petroleum Gas (lp gas, sometimes called lpg) Colorless, odorless and non-toxic gas. It is separated from wet natural gas, light crude oil and oil-refinery gases. Main Gas Burner Device for the final conveyance of gas or a mixture of gas and air to the combustion zone. The gas burners in gas-burning appliances are made of either aluminized steel or stainless steel. They come in many different styles.The parts of the main burner include: the burner orifice, a mixing tube, and the burner head. Manifold Pressure The amount of wc inches that can be supported by different types of gas: the manifold pressure for natural gas is 3.5" wc and for LP gas the manifold pressure is 11" wc. Mantel An ornamental facing surrounding the fireplace or simply a shelf above a fireplace. Metal Liner Used primarily with fireplace inserts and placed inside an existing chimney (usually masonry) to reduce the diameter of the flue for more rapid exit of smoke and combustion gases. Also used when an existing chimney is unlimited or deteriorating. Millivolt A unit of electromotive force equal to one thousandth of a volt. National Fuel Gas Code A standard for the installation of gas hearth appliances to be used in the absence of local codes. Natural Draft (B-vent) Appliance An appliance that takes in combustion air from the home and vents products of combustion outside of the home. Natural Gas (NG) Colorless, highly flammable gas consisting mainly of methane. A highly popular gas because of its flammability and high energy value. This naturally occurring mixture of hydrocarbon and non-hydrocarbon gases is found in porous geologic formations beneath the earth's surface, often in association with petroleum. Orifice The opening in a cap, spud or other device whereby the flow of gas is limited, and through which the gas is discharged to the burner.Two types of orifices include main burner orifices and pilot burner orifices. Main burner orifice: either a plug or cap type. Oxygen Depletion Sensing Device This device on a spill switch senses the lack of oxygen and shuts down the electrical flow, shutting off the appliance. Pellets Are made of 100% wood sawdust with no additives. The sawdust in pellets is a manufacturing by-product otherwise destined for landfills. Piezo Starter Red button that places pressure on the crystal in the standing pilot system. Pilot A small flame used to ignite the gas at the main burner. Propane A liquefied petroleum gas (see LPG) containing more heat value than natural gas. It is colorless, odorless and non-toxic. Regulator Usually it is a part of the combination valve. It reduces the pressure to the appropriate level for the type of gas used in the appliance. Sealed Combustion Vent A type of double-walled special vent supplied by the manufacturer that normally vents through a side wall in a horizontal position. The inner surface removes the flue gases and the outer container provides for passage of combustion air. Seasoned Refers to fuel wood that has been allowed to dry before burning. Seasoning generally takes six to twelve months. Wood burns much easier when its moisture content has been reduced. Freshly cut wood contains over 20 percent water. Standing Pilot Ignition A means to light the main gas burner through the use of a standing pilot light. Therm A unit of heating value equivalent to 100,000 British thermal units (BTUs). Thermo Sensor Automatically turns blower on and off. Top Vent Fireplaces A gas appliance that vents off the top of the unit using a type B-vent, provision for outside air. Unvented or Vent-Free An appliance that draws combustion air from inside the home. The appliance is designed to burn so efficiently that it eliminates the need for venting. Vent-Free Gas appliance that has no need for a flue. Vented Wall Furnace A self-contained vented appliance complete with grills or equivalent, designed for permanent attachment to the structure and furnishing heated air by gravity or fan. Venting To provide an exit. In gas appliances, venting is used to distribute air through a specific environment to maintain temperature there and to remove dangerous combustion by-products. Venting System A continuous open passageway from the flue collar or draft hood of a gas-burning appliance to the outside atmosphere for the purpose of removing flue or vent gas. It is usually composed of a vent or a chimney and vent connectors assembled to form the open passageway. Wall Thermostat A heat sensitive electrical switch that maintains the temperature and controls the on-off action of the heat source. NOTE: thermostats should only be used with gas appliances that have been tested and listed for use with thermostats.