Glossary of Terms

Better understand phrases frequently associated with the fireplace industry


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

B Vent Fireplace

B Vent gas fireplaces use air from inside your home to fuel combustion and rely on the buoyancy of hot gases to vent exhaust through dedicated pipe systems.


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

BTU (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.


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

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.


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.

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. Center is exhaust and outer donut area is fresh air.

Co-Linear Direct Vent

A Direct Vent system consisting of two separate pipes. 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.

Convective 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.

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. No chimney required.


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


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

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.


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

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.

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.


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


Reduce surface temperatures for heat sensitive material directly above the fireplace.

Liquefied Petroleum Gas (LPG)

Colorless, odorless, and non-toxic gas separated from wet natural gas, light crude oil, and oil refinery gases.

Manifold Pressure

Gas pressure between the combination valve and the burner orifice.


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

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.

Natural Gas (NG)

Clean-burning fossil fuel available in vast quantities throughout North America and delivered to homes via an extensive pipeline network.

Pilot Light

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


Facilitates excess warm air circulation back into the room a higher elevation.

Pressure Test

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


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


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.

Remote Control

A wireless handheld remote control system which allows the user complete control of the fire from anywhere in the room.

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.

Steady State Efficiency

The ratio of the heat or BTU output vs. the heat or BTU input under steady conditions.

Thermal Efficiency

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


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.


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.

Unvented (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.


Standard equipment on most Valor models - controls the comfort, convenience and aesthetics you want from your Valor gas fireplace. See Modulating Control.

Zero Clearance Fireplace

Factory built units for installation into combustible construction.



About Valor

Warming homes since 1890, Valor continues to set new standards in gas fireplace efficiency, comfort control and fashionable design. Our mission is to be a leader in the design and production of innovative, energy-efficient home comfort products.