Common Terms

Glossary of common terms

BTU (British Thermal Unit) 

- The quantity of heat required to raise the temperature of one pound of fresh water one degree Fahrenheit. 

Burner 
- The essential part of a gas appliance where air and gas combine before the combustion phase.

B Vent 
- Double-walled, galvanized metal outer pipe with an aluminum inner pipe. Used for natural vent gas appliances, and must terminate vertically.

Ceramic Fiber 
- A material used to make gas logs and fireplace accessories; it is able to withstand very high temperatures.

Damper 
- A valve, usually a moveable metal plate, for controlling flow of air or smoky by-products of combustion.

Direct Vent 
- A sealed heating system, whereby all combustion air is supplied from outside the building, and all flue gases are returned to the outside. May terminate horizontally. 

Emissions 
- Smoke, creosote and other by-products of combustion. 

Freestanding Stove 
- Heating appliances that are self-contained, normally on legs. 

Fireplace 
- Any enclosure, open in the front, for burning fuel. Wood burning rated fireplaces may burn either solid fuel, or be fitted with gas logs or certain fireplace inserts. Gas fireplaces contain a burner apparatus and artificial logs. 
Fireplace Insert 
- Appliance designed to be installed, partially or fully, into the firebox of an existing masonry or factory-built fireplace, and which must be vented.

Gas Logs 
- Used in a fireplace to take the place of wood, consisting of a burner and log assembly.

LP 
- Liquid Petroleum fuel, also called propane.

Millivolt 
- Unit of electricity (equal to one-thousandth of a volt of direct current) that, in conjunction with the pilot flame, operates the valve on certain gas appliances.

Natural Vent 
see B Vent

ODS (Oxygen Depletion Safety Valve) 
- A device used with all vent-free stoves, fireplaces and logs that shuts the unit down if the oxygen level in the room falls below 18%. ANSI indoor air standards require a minimum oxygen level of 15% for safety reasons.

Pilot 
- A small flame used to ignite gas at the main burner. May be standing (constant) or intermittent (usually requires electricity.)

Propane 
- LP fuel

Vent-free Heater/Fireplace 
- A gas appliance that does not require a flue system (chimney or vent.)

Zero Clearance 
- A term often used to generically describe most factory-built fireplaces. It refers to a quality of the fireplace whereby enough insulation is incorporated so that the base, back and sides can be safely placed in direct contact with combustible floors and walls.