Stove Terms Glossary

Air Shutter
An adjustable restrictor partially covering an opening at the orifice end in the tube supplying gas to the burner. It meters the amount of primary air drawn into the tube that mixes with the fuel gas before the mixture goes to a main burner and is ignited.  The amount of air mixed with the fuel gas determines how cleanly, and efficiently the mixture burns - also for maximizing the ambiance of the flames.

Air Wash
As the primary air enters the stove, it is directed through passages where it is pre-heated and directed down the glass surface on the inside of the front door. The constant "washing" of that hot air over the glass helps keep soot and creosote from building up on the glass. "Infrared Reflective Ceramic" glass used in conjunction with the air wash helps keep the inside surface of the glass hotter and cleaner for maximum fire enjoyment.

A recessed or built in area of a room usually including two sides and a top.

Factory built, double-wall metal pipe for venting gas appliances with draft hoods and other appliances listed for use with Type B Gas Vent. It consists of an aluminum inner wall and a galvanized or galvalum outer wall with a dead air space between the walls.

Back drafting (back puffing)
A term to describe the condition when the flow of combustion products in a venting system reverses direction.
Usually caused by errant wind gusts, or negative pressure situations in the structure. More common in installations with poor draft conditions.

BTU (British Thermal Unit)
The amount of energy it takes to heat one pint of water one degree Fahrenheit.

Carbon Monoxide
What is it? Carbon Monoxide (CO) is a poisonous, odorless, tasteless gas formed by the incomplete combustion of carbon based fuel, or the reduction of carbon dioxide. Formation in dangerous quantities is uncommon in wood burning appliances. Formation is more common in coal, or charcoal burning appliances. Typically found where a hydrocarbon based fuel burning appliance or motor is improperly maintained, vented, or used.
At what level does carbon monoxide become toxic?
For healthy adults, CO becomes toxic when it reaches a level higher than 50 ppm (parts per million) with continuous exposure over an eight hour period. When the level of CO becomes higher than that, a person will suffer from symptoms of exposure. Mild exposure over a few hours (a CO level between 70 ppm and 100 ppm) include flu-like symptoms such as headaches, sore eyes and a runny nose. Medium exposure (a CO level between 150 ppm to 300 ppm) will produce dizziness, drowsiness and vomiting. Extreme exposure (a CO level of 400 ppm and higher) will result in unconsciousness, brain damage and death.
How to avoid carbon monoxide poisoning
- Have a qualified technician install and regularly inspect all fuel burning appliances
- Regularly inspect fireplaces and chimneys to ensure proper ventilation
- Never use a gas or charcoal barbeque indoors
- Never run a generator anywhere inside your home or garage. Never run a car, gas lawnmower or snow blower in a closed garage.
- Install carbon monoxide detectors in your home.

Cast Iron
A durable material used in many stoves. Cast iron is made by remelting pig iron, often along with substantial quantities of scrap iron and scrap steel, and taking various steps to remove undesirable contaminants such as phosphorus and sulfur.
Depending on the application, carbon and silicon content are reduced to the desired levels, which may be anywhere from 2 to 3.5% and 1 to 3% respectively. Other elements are then added to the melt before the final form is produced by casting in molds.
Cast iron must typically be painted, or enameled to prevent surface oxidation (rust).

Catalytic Combustor
A specially coated ceramic "honeycomb" often used to reduce flue gas particulate and other emissions.

Chimney Connector
The pipe that physically connects a fuel-burning appliance to a chimney, or chimney liner. Never use connector pipe as a chimney - it cannot survive the intense heat of a chimney fire, and does not meet the code requirements for a class A chimney.

Class "A" Chimney
A residential type chimney suitable for use at 1000ºF, which complies with the optional 10-minute 2100ºF test. Such chimneys are labeled as Type HT and are required for certain solid-fuel applications.

Close Clearance Stove Pipe
A double wall stove pipe usually consisting of an inner pipe, a small dead air space and an outer pipe. Used as a chimney connector it can reduce the necessary clearances to a combustible surface considerably over single wall stove pipe.

Coaxial Venting System
A Direct-Vent venting system using a larger outside diameter pipe for the fresh air intake and a smaller diameter pipe inside the outer pipe for exhaust gases. Usually the inside pipe is either 4" or 5" in diameter while the outside pipe is either 6¨ý" or 8" in diameter. Typically used with appliances that draw their combustion air from the outside of a structure.

Collinear Venting System
A Direct-Vent venting system using two separate pipes running next to each other. Normally one of the pipes (exhaust) is 3" or 4" in diameter, while the other (intake) is smaller. May be utilized in forced draft applications - such as pellet burning appliances.

Combustible Material
Material made of, or surfaced with wood, compressed paper, plant fibers, plastics, or other material that can ignite and burn, whether flame proofed or not, whether plastered or unplastered. For example: painted drywall is a combustible material since the paint, and paper on its face can burn even though the gypsum core does not burn.

The transmission of heat by air or liquid movement. Heated air/liquid is less dense than cooler surrounding air/liquid causing it to rise. As the heated air/liquid rises higher or travels further it eventually begins to give up its heat and to cool, and starts to fall as its density increase. This process creates circulation in a system (air in a room or structure, water in a pipe loop). An older term for convection is 'Gravity Heat'.
Convection can be made more efficient, or controllable by use of circulators in the system - blowers on stoves or pumps in heating pipe systems to increase flow. Contrary to common belief, circulators do not significantly increase the amount of heat stripped off the heat source - they just allow you to put it where you want, or need it.

Chimney and stove pipe deposits originating as condensed wood smoke (including vapors, tar and soot). Creosote is often initially liquid, but may dry to pryrolze to a flaky or solid form.
Creosote forms when cordwood or pellets are burned inefficiently, or the fuel is green, or wet (high moisture content). Cool, exterior chimneys are also prone to creosote formation due to rapid cooling of flue gasses as they contact the inside surface of the flue liner - even if the stove is efficient and the wood being burned is dry.
Creosote deposits can ignite if allowed to accumulate, and will burn fiercely at very high temperatures. Temperatures reached can significantly damage a chimney, or cause a structure fire. Inspect your chimney regularly, and have any deposits removed promptly.

A condition when the air pressure in the home is less than the air pressure outside the home. It can be caused by inadequate ventilation or the use of other home appliances such as a dryer, or an exhaust fan in the kitchen or bathroom. It leads to back drafting or spillage in a conventional vent system. Depressurization is common in new, tightly constructed homes. Also known as Negative Pressure.

A venting system in which 100% of the combustion air is drawn from the outside of the structure, and all the combustion products are returned to the outside. Negates the negative pressure, or de-pressurization issues caused by modern 'tight' construction methods.

Double Heat Exchanger
What is a heat exchanger: A heat exchanger helps to quickly transfer heat from inside the firebox into the room, before the heat goes up the chimney. The better and more numerous the heat exchanger(s), the more efficient the stove. What is a double heat exchanger? Most gas-fired heaters have a single heat exchanger. Some gas stoves are unique in that they have double heat exchangers. The first is the standard convective air chamber surrounding the firebox and the second heat exchanger consists of the massive, finned, cast iron unit attached to the top of the stove. The shorter set of fins extend downwards into the firebox, directly into the path of the flames and hot flue gasses. The longer fins face upwards, directly into the path of convection air heating your room. What is the result? Our finned cast iron heat exchanger helps to quickly and efficiently transfer copious amounts of heat from the firebox into the living space. The result is high efficiency and maximum output for your heating dollar.

The pressure difference between the hot flue gases inside the venting system and the cool air surrounding the venting system. Hot flue gasses have a lower density than the cool air surrounding the chimney, and tend to rise. This rising column of gasses creates a suction effect at the lower end of the chimney providing there is sufficient make up air in the structure. Newer, energy efficient homes are tighter, and usually contain multiple appliances that use fans for venting exhaust, or other air/smoke (power vented water heaters, dryers, kitchen stove vents, etc.). These can all create negative pressure in the structure too great for the natural draft formed in the chimney to overcome, and can cause difficult starting, poor performance, and back drafting through the stove. Outside air kits can help alleviate this problem by providing the stove's combustion air supply from the exterior of the structure (providing all connector joints, and cleanout doors inside the structure are tightly sealed).

EPA Phase II
In 1988 the federal government issued strict emission controls on woodstoves. These standards were instituted in two phases. All stoves built after July 1, 1992 must meet the stricter standards outlined in the second phase of that regulation.

Factory-Built Chimney
A chimney composed of listed, factory-built components 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.

Factory-Built Fireplace
A fireplace composed of listed, factory-built components assembled in accordance with the terms of the listing.

The window on the door(s), front, or sides of your gas or woodstove is not actually glass at all. It is a technologically advanced ceramic material, much stronger than standard window glass; able to withstand temperatures of over 2000º F, and rapid temperature changes with no decrease in strength or durability.

Hearth Extension
A non-combustible, usually insulated surfacing applied to the floor area extending in front of and to the sides of the hearth opening of a fireplace or a fireplace stove. The extension provides for code required protection distances should your existing hearth not meet them, or just for additional safety as desired.

Heat Life
The length of time a stove stays hot and radiates heat after burning a load of fuel.

Equipment, materials, or services included in a list published by an organization acceptable to the authority having jurisdiction. The listing states either that the equipment, material or service meets identified standards or has been tested and found suitable for a specific purpose.

Masonry Chimney
A field-constructed chimney of solid masonry units, including brick, stone, listed masonry material, usually lined with fire clay flue liners.

Millivolt (Mv)
Unit of electromotive force equal to one-thousandth of a volt.

Negative pressure
See depressurization

NFPA 211
National Fire Protection Agency standard #211 "Standard for Chimneys, Fireplaces, Vents and Solid Fuel-Burning Appliances".

National Fire Protection Agency standard #54 "National Fuel Gas Code" .

Non-catalytic woodstoves have a series of secondary air tubes under the baffle in the top of the firebox. These tubes draw in a precise amount of heated air, inject it into the fire and combustion by-products and actually cause any particles and gas in the smoke to burn. Consequently your stove is helping to keep our environment clean while you enjoy the benefit of more heat out of less wood.

Noncombustible Material
A material that, in the form in which it is used and under the conditions anticipated, does not ignite, burn, support combustion or release flammable vapors, when subjected to fire or heat.

Oxygen Depletion Sensing (ODS) Pilot Assembly
A pilot burner found in Vent-Free appliances, which can sense and respond to changes in oxygen levels. It consists of an orifice for gas flow and a bimetallic air shutter, a thermocouple and a spark electrode. Before the oxygen level reaches 18% the flame lifts off and causes the thermocouple to cool shutting off the gas flow to the burners.

Piezo Electric Igniter
A device which delivers an igniting spark by mean of pressure on a crystal.

The transmission of heat via radiant energy.

A manual, or electrical device for controlling and maintaining a uniform, or variable outlet of fuel gas pressure. Usually part of a combination gas valve.
For example: if you burn propane, you will have a high pressure regulator on the tank itself, and a low pressure regulator on the exterior of your home. The low pressure regulator reduces the line pressure from about 15 psi coming from the tank to the about 0.4 psi (11 inches water column) normally used by your appliances.

Sealed Combustion System
A Direct-Vent system. A self-contained combustion system in which all the combustion air is drawn from the outside a structure and all the combustion product is returned to the outside. The combustion system does not interact with the air inside a structure.

Sediment Trap (Drip leg)
A required part of every gas installation, which allows a contaminant collection point ahead of the appliance for moisture, and foreign particles (i.e. copper sulfide) that may be in the fuel gas. A sediment trap in the gas line helps minimize, or prevent main burner and pilot burner fouling, and corrosion. Plus the trap helps slow accumulation of fuel gas contaminant deposits on firebox interior surfaces - to include the glass.

A metamorphic rock formed millions of years ago under intense heat and pressure. It evolved from a molten state deep within the earth with an unusually stable composition. Unlike other stones, it can withstand fire and dramatic changes in temperature. Other stones, such as granite and marble, also hold and radiate heat, but only soapstone is able to withstand direct flames indefinitely.

Spill Switch
A heat activated safety sensor, which detects flue gas flow reversal, which will shut an appliance off. Typically found in B vented fuel gas burning appliances.

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 Millivolts between 25-30 millivolts. Used to power the gas safety valve.

A number of thermocouples connected in series to produce more DC Millivolts than a single thermocouple. Depending on size, the DC Millivolts range between 250 and 750 millivolts.

Special metal or clay sleeves for wall and ceiling penetrations when installing a venting system to ensure that the proper clearance away from combustibles is maintained.

Vent-Free or Ventless
Gas appliance systems where all combustion byproducts (mostly water vapor and carbon dioxide) are released into the same room environment as the appliance.

Water Column (W.C.)
Unit of measurement for gas pressure in inches of water. Approximately 28 inches water column equals one psi.

Zero-clearance fireplace
See Factory-built Fireplace.