Fireplace Glossary

ANSI: American National Standards Institute. The organization responsible for federal national standards system, consisting of hundreds of companies and over 200 trade, technical, professional, labor and consumer organizations that meet and solicit information and guidance, then publish updated and/or revised safety standards.
Ash Pit/Ash Drawer: sometimes fitted with a removable container, the area beneath a combustion chamber in a wood burning fireplace or wood stove that catches and contains ashes until removal.
Asphyxiation: fatality/death as the result of being deprived of oxygen; suffocation (in particular relation to fires/flames:  due to smoke inhalation and/or the presence of carbon monoxide and/or inadequate amount of fresh air circulation).
Thermostat: a mechanical device (e.g., bi-metal, electronic or other) that monitors/measures room temperature and will automatically operate a heater to maintain a relatively constant room temperature.  Most thermostats can be manually adjusted by the user to raise or lower the ambient temperature for either lower or warmer room temperature settings.
Blower: an electric motor driven fan that circulates air.  In particular relation to a heater, to move/circulate warmed air. 
B-Vent: a type/style of metal vent/chimney pipe used to exhaust products of combustion from many gas appliances; sometimes used to describe a gas fueled heater or gas fueled fireplace that must be vented to the outdoors.  B-Vent heaters/fireplaces draw combustion air from inside the home through openings/ports in the appliance.  (Also called Natural vent).
Btu: British Thermal Unit; a measurement of heat or heating power (the amount of energy required to raise one pound of water by one degree F). Subject to different amounts of insulation, air circulation, and geographic location ... 5,000 Btu's is typically thought of as being capable of being able to warm about 400 square feet. 
Burner: In relation to a gas heating or a fireplace appliance, the appliance component  (typically steel or cast iron, or other) where the final mixture of gas fuel, air and a flame ingnition source meet to provide fire to product heat / combustion. 
Catalytic Combustor:  Used in some wood burning appliances, these typically are honeycombed ceramic devices that are coated with a catalyst (sometimes platinum) that lowers the temperature at which combusion can take place.  In a catalytic appliance, most or all of the products of combusion (smoke) passes through the catalyst and combusts further, releasing more heat, before exiting the appliance. This action allows wood to burn slower, longer and therefore, more efficiently, and the smoke/fumes that would normally be released via the chimney are burned more effectively releasing fewer pollutants.
Certified Chimney Sweep: a trained and licensed professional practicing proper inspection and cleaning of fireplaces and chimneys.
CFM: Cubic Feet per Minute. This is the amount of air that a blower will move.
Chase:  a structure (e.g., wall) built around and enclosing at least a portion of a chimney either inside or outside a building.
Chimmey:  a component of an appliance venting system through which exhaust/flue gases are vented to the outdoors.  To aid in the venting action and to protect combustible surfaces around the appliance and its exhaust.  Typically, a chimney includes a vertical shaft enclosing at least one flue, the design of which results in a natural draft to aid in the safe exhausting the products of combustion to the outdoors.
Clearances or Minimum Clearances:  appliance labels and installation instructions as well as fire and building codes state that there should be a certain distance (clearance) between a fireplace, stove or other heating appliance and any combustible objects such as furniture, floors, walls, etc.  These requirements should always be followed.
Damper: a device used to reduce or close the opening between a firebox and its flue/chimney.
Direct-Vent: also known as a balanced flue venting system.  A gas appliance where the exhaust is balanced with combustion air intake (air from outdoors).  Can be either colinear or coaxial - can be either through a roof or through a wall.
Efficiency: in short, the percentage of heat that goes into the room instead of out the chimney or flue.
Electric Igniter: a device that ignites the burner or pilot which requires electrical currents in lieu of a match.
Fireback: a protective, heat-resistant insert for the rear interior of the fireplace.
Fire box: the chamber of the fireplace that contains the fire.
Flue: a pipe or channel for moving smoke from the fireplace to the chimney and to the outdoors.
Furnace: a central heating appliance that supplies hot air through ducts.
Grate: an iron frame that holds burning fuel for the fire.
Hearth: Non-combustible material (brick, stone, etc.) at the floor, usually extending out from the wall and to either side of a fireplace opening.
Liquefied Petroleum Gas (LPG): (AKA LP or Propane) a colorless, odorless, and non-toxic gas separated from wet natural gas, light crude oil, and oil refinery gases. Odorants are added to help identify gas leaks.  
KWH: kilowatt per hour (equals 1000 watts per hour). An energy measurement for electricity.
Mantel: generally a wood or stone structure normally including a projecting shelf above a fireplace opening. A 'full mantel' typically has "legs" from the shelf down to the floor beside the fireplace opening.  A 'cabinet mantel' typically is deep front-to-back and houses/conceals the top and sides of a gas or electric fireplace (aka, fireplace insert) that is placed on the floor, backed up to a wall, rather than being recessed into the wall.
Mcf: Thousand cubic feet.
Millivolt: a safety control valve system that uses a small electromagnet that operates in conjunction with heat from a pilot light that will only allow gas to flow when the pilot light is properly lit and operating.   A millivolt system is not dependent on household electricity.
Peninsula fireplace: a fireplace with 3 open sides normally built into a half or partial wall.
Rear Vent: a fireplace in which the flue is attached to the back (rear) side of the fireplace or stove. Standing pilot light: a pilot light which is remains lighted at all times until mechanically turned off.
Standing safety pilot:  a manual or remote controlled gas valve which shuts off the flow of all gas to the appliance if the pilot light goes out.
Spillage: this term refers to fireplaces or gas appliances with vented (chimney/flue) systems. When a chimney flue becomes blocked (or if the flue is improperly designed or constructed) combustion by-products will not be vented to the outdoors and, therefore, 'spill' into the room. This can be dangerous as carbon monoxide may be one of the by-products leaking back into the home. Carbon Monoxide gas is odorless, colorless and deadly.
Surround: the area along the top and sides surrounding the fireplace itself; it usually includes the mantel and hearth.                                                                                 
Thermocouple: a component of the safety system, it is a device consisting of two dissimilar metals joined together at one end (its hot junction). When the hot junction is heated, the thermocouple produces a small amount of DC voltage that is used to power thermoelectric gas valves.  If there is no pilot generating heat, the gas supply is shut off.
Top-Vent: a fireplace in which the flue is attached to the top of the fireplace or stove.
Ventless: (aka Unvented, aka, Vent-free) Typically, a gas-fueled appliance or fireplace that requires no chimney, flue or venting since clean combustion is maintained within the system.  An oxygen-depletion system (ODS) is required on residential Ventless (vent-free) gas appliances to shut off the flow of gas if there is inadequate fresh air to support safe and clean combustion.