Glossary of Terms

AIR CIRCUALTION—The natural or mechanically induced movement of air through an enclosed space. Natural ventilation results from thermal effects such as those from a vent, or may be caused by wind, or both.  Their effectiveness is aided by opening or closing windows. Much greater control can be achieved with mechanical systems such as blowers or fans.

AIR INFILTRATION—Typically, the passing of air into the house through small cracks or gaps inherent to the structure. Affected by temperature differences between the inside and outside of the structure, and air pressure factors (e.g. wind, the operation of solid fuel appliances, or electrical appliances such as fans).

ANSI—American National Standards Institute. The coordinating organization for federal national standards system, consisting of 900 companies and 200 trade, technical, professional, labor, and consumer organizations.

APPLIANCE REGULATOR—The appliance component, usually part of the combination valve, that maintains constant gas pressure.

APPROVED—Acceptable to the authority having jurisdiction.

AUTHORITY HAVING JURISDICTION—The organization, office, or individual responsible for approving equipment, installation, or procedure.

B VENT GAS—Listed, factory-built, double wall metal pipe for venting appliances with draft hoods and other appliances listed for use with Type B Gas Vent.

BLOWER — A motor driven fan used to improve air circulation.  While a blower may be standard on some appliances, they are sometimes sold as an accessory item. Blowers may have either automatic or manual controls, depending on their design.

BTU OR 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.

BURN RATE—Combustion rate, usually expressed in pounds of fuel consumed per hour.

BUTANE—A colorless, odorless, non toxic gas; not generally used in hearth appliances.

CALORIFIC—Energy Value.

CARBON DIOXIDE—CO2. Colorless, odorless, noncombustible gas produced by the complete combustion of carbonaceous fuel; is non-toxic. A gaseous product of combustion.

CARBON MONOXIDE—CO. Colorless, odorless, combustible, and toxic gas produced by the incomplete combustion of carbonaceous fuel, resulting in the combining of 1 rather than 2 oxygen atoms with 1 carbon atoms. A toxic, combustible gas formed in incomplete combustion.

CHIMNEY—A portion of the venting system, through which flue gases are vented to the outdoors and by which penetrated combustible surfaces are protected; a primarily vertical shaft enclosing at least one flue, the design of which results in a natural draft.

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 or via short ducts. Also see circulating stove.

CLEARANCES—Minimum distance, composed only of an air space, which must be maintained between a heat source such as an appliance or vent and combustible surfaces.

CLIMATE CHANGE—A term used to refer to all forms of climatic inconsistency, but especially to significant change from one prevailing climatic condition to another. In some cases “climate change” has been used synonymously with the term “global warming.” However, scientists tend to use the term in a wider sense inclusive of natural changes in climate, including climatic cooling.

COLD JUNCTION—Non-heated end of the thermo-couple/thermopile.

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, chimney connectors, steam and hot water pipes and warm air ducts. Such material shall be considered as combustible even though flame proofed, fire retardant treated, or plastered.

COMBUSTIBLES—(as applied to walls, floors and ceilings in the context of wood heater clearances for safety). Constructed of or surfaced with wood, paper, natural- or synthetic fiber cloth, plastic or other material which will ignite and burn, whether flame proofed or not and whether plastered or un-plastered. Combustibility is a relative concept. This definition is adapted from the definition in NFPA booklet glossary of terms relating to heat-producing appliances.

COMBUSTION—The process of burning, or oxidation accompanied by heat. When sufficiently rapid, also accompanied by light.

COMBUSTION CHAMBER—Area where mixing of combustion air and fuel occurs.

COMBUSTION EFFICIENCY—The percentage of the total energy content of the fuel consumed that is converted to heat in the fire.

CONDUCTION—Direct transfer of heat from one material to another.

CONTROLLED COMBUSTION—Complete burning of fuel with a steady flame when fuel and air supplied at proper rate.

CONVECTION—The transmission of heat by the circulation of a fluid (air or water) caused by differences in temperature (and therefore density).

CONVECTION HEATER—A heater that distributes most of its energy by heating the air circulating in the area.

CSA CERTIFIED —CSA certifications are used and accepted across North America and around the world, on over 1 billion products. In the U.S., CSA International is recognized by the Occupational Health and Safety Administration (OSHA) as a Nationally Recognized Testing Laboratory (NRTL). CSA International tests to applicable U.S. and Canadian standards, which include ANSI, UL, CSA, NSF, and others.

CUBIC FOOT (natural gas) —A unit of volume equal to 1 cubic foot at a pressure base of 14.73 pounds standard per square inch absolute and a temperature base of 60 degrees F.

DEGREE DAYS, HEATING—A measure of how cold a location is over a period of time relative to a base temperature, most commonly specified as 65°F. The measure is computed for each day by subtracting the average of the day’s high and low temperatures form the base temperature (65°F) with negative values set equal to zero. Each day’s heating degree days are summed to create a heating degree-day measure for a specific reference period. Heating degree days are used in energy analysis as an indicator of space heating energy requirements.

DEW POINT—The temperature at which liquid water forms from vapor.

DIAPHRAGM—Part of pressure regulator which responds to changes in gas pressure to maintain constant outgoing pressure.

DIESEL FUEL—A fuel composed of distillates obtained in petroleum refining operations or blends of such distillates with residual oil used in motor vehicles. The boiling point and specific gravity are higher for diesel fuels than for gasoline. 1): A light distillate fuel oil that has distillation temperatures of 550 degrees Fahrenheit at the 90-percent point and meets the specifications defined in ASTM Specification D 975. 2): A fuel that has a distillation temperature of 640 degrees Fahrenheit at the 90-percent recovery point and meets the specifications defined in ASTM Specification D 975.

DIRECT SPARK IGNITION—A type of intermittent ignition system that ignites the gas directly at the main burner by means of a spark.

DRIP—In gas piping, a tee device used to collect condensate from gases. Installed so that they can be serviced to remove condensate. Also known as drip leg.

EFFICIENCY—The percentage of heat that goes into the room instead of up the chimney. 70-80% efficiency is optimal.

ELECTRICITY—A form of energy characterized by the presence and motion of elementary charged particles generated by friction, induction or chemical change.

ELECTRONIC SNIFFER—A device which emits a loud, piercing noise in the presence of very small amounts of certain gases. Used in gas supply line and appliance leak detection.

ENERGY—The capacity for doing work as measured by the capability of doing work (potential energy) or the conversion of this capability to motion (kinetic energy). Energy has several forms, some of which are easily convertible and can be changed to another for useful for work. Most of the world’s convertible energy comes from fossil fuels that are burned to produce heat that is then used as a transfer medium to mechanical of other means in order to accomplish tasks. Electrical energy is usually measured in kilowatt hours while heat energy is usually measured in British Thermal Units (BTU’s).

ENERGY COSTS—The monetary costs associated with the purchase of energy sources such as home heating fuels, electricity, gasoline, etc. However, other costs such as weatherization or the purchase of more energy efficient products are indirect long term investments also associated with ENERGY COSTS.

ENERGY EFFICIENCY—The percentage of the total energy content of the fuel consumed that becomes useful heat in the house.

ENERGY SAVINGS—The monetary savings realized through such activities as zone heating, weatherization, the use of alternative energies, etc. See DOE’s website for additional information.

ETL LISTED —The ETL Listed Mark is proof of product compliance (electrical, gas, and other safety standards) to North American safety standards. Authorities Having Jurisdiction (AHJ’s) in 50 states and Canada and retailers accept the ETL Listed Mark as proof of product safety.  ETL mark from Intertek is found on more than 80,000 products in North America.

FACTORY BUILT FIREPLACE—Prefabricated metal fire chamber and its chimney, commonly called zero clearance. Consists of listed manufactured components that are assembled in accordance with the terms of the listing to form the completed fireplace.

FIREPLACE—An enclosure, open in the front for burning fuel. Solid fuel fireplaces may contain and vent gas log sets or fireplace inserts. Gas fireplaces are metal appliances open in the front and containing artificial log sets.

FIREPLACE (ELECTRIC)—A decorative appliance that uses a light bulb and other means to create an artificial flame that mimics a wood burning fire. Most of these appliances also employ small electric heaters to create heat.

FIREPLACE (GAS) —A Liquid Propane or Natural gas appliance designed to look like a wood burning fireplace, providing both heat and decorative flame. These are generally comprised of artificial logs, mounted atop a gas burner assembly, within a metal enclosure that is attached to a decorative wooden mantel or other surround.

FIREPLACE, ZERO CLEARANCE—A factory-built metal fireplace with multi-layer construction providing enough insulation and/or air cooling so that the base, back, and in some cases sides, can safely be placed in direct contact (zero clearance) with combustible floors and walls.

FIRE RESISTANCE RATING—The time a material will withstand, without igniting, flame and heat as specified by code and specific test conditions.

FLAME IMPINGEMENT—The striking of flame against an object, such as flame impingement on a log in a gas fireplace.

FOSSIL FUEL—An energy source formed in the Earth’s crust from decayed organic material, such as petroleum, coal and natural gas.

FREESTANDING GAS APPLIANCE—An appliance with gas burning log set that has the appearance of a solid fuel appliance that is placed away from walls in a dwelling.

FREESTANDING STOVE—Heating appliance normally on legs or a pedestal that occupies an area roughly equal to that of an easy chair.

FUEL OIL —A liquid petroleum product less volatile than gasoline, used as an energy source.  1): A light distillate fuel oil that has distillation temperature of 400 degrees Fahrenheit at the 10-percent recovery point and 550 degrees Fahrenheit at the 90-percent point and meets the specifications defined in ASTM Specification D 396. It is used primarily as fuel for portable outdoor stoves and portable outdoor heaters. 2): (heating oil): A distillate fuel oil that has a distillation temperature of 400 degrees Fahrenheit at the 10-percent recovery point and 640 degrees Fahrenheit at the 90-percent recovery point and meets the specifications defined in ASTM Specification D 396. It is used in atomizing type burners for domestic heating or for moderate capacity commercial/industrial burner units.

FURNACE—A central heating appliance that supplies hot air, through ducts, to the house.

FUSE—A device containing an element that protects an electric circuit, by melting, to open the circuit when overloaded.

GAS FIREPLACE INSERT—A gas appliance designed to be installed within an existing fireplace. Usually gas logs within a metal enclosure that surrounds the logs and covers the space between itself and the fireplace opening.

GAS REGULATOR—A pressure regulator who’s primary function is to match the flow of the gas to the demand for gas through the system. If too much pressure is present the regulator will close, thereby stopping the flow of all gas to the appliance.

GAS WELL—A well, completed for the production of natural gas from one or more gas zones or reservoirs.  Vent Free Gas appliances will not operate correctly on gas coming directly from a gas well. This type of fuel is sometimes referred to as WELL HEAD GAS.

GRATE—A metal plate with engineered holes or a framework of metal bars used to hold gas logs, etc.

GROUNDED—The metallic connection of an electric circuit to the earth by means of a water main or special rod driven into the ground.

HEAT CONTENT—The amount of heat energy available to be released by the transformation or use of a specified physical unit of energy form (e.g. a ton of coal, a barrel of oil, a kilowatt of electricity, a cubic foot of natural gas, or a pound of kerosene) (The amount of heat energy is commonly expressed in British Thermal Units, BTU’s). Note: Heat content of combustible energy forms can be expressed in terms of either gross heat content (higher or upper heating value) or net heat content (lower heating value), depending upon whether or not the available heat energy includes or excludes the energy used to vaporize water (contained in the original energy form or created during the combustion process). The US Energy Information Administration typically uses gross heat content values.

HEAT LIFE (THERMAL CAPACITANCE)—The length of time a stove stays hot after burning.

HEAT LOSS CALCULATION—Calculation to determine house BTU loss; factors include conduction through construction materials, air infiltration losses and the difference between actual or projected outside temperatures and desired temperatures inside the house. Used for determining necessary heat output from the heating appliance.

HEAT OUTPUT—The amount of usable heat produced by a heating appliance; expressed in BTU’s (for most conventional fuel appliances) or watts per hour.

HEAT VALUE—Amount of heat potential of one cubic foot of gas when burned. Also known as calorific value.

HEATING APPLIANCE—An appliance used to produce heat for residential, commercial or industrial applications.

HEATING COSTS—The monetary costs directly associated with home heating, generally fuel costs. However, other costs such as weatherization, updating, replacing or adding a new heating appliance are indirect long term investments also associated with HEATING COSTS.

HOT JUNCTION—Joined, heated end of thermocouple/thermopile.

HOT SURFACE IGNITION—Type of electric (intermittent) ignition system in which a glow bar is heated by electrical means to a temperature of about 2500 degrees F. to provide the heat to ignite the fuel.

IGNITION SYSTEMS—Devices that ignite the pilot burner and/or the main burner assembly.

INCOMPLETE COMBUSTION—Improper air/fuel mixture or inadequate temperatures resulting in less than complete burning of fuel. May produce aldehydes and/or carbon monoxide.

INFRARED RADIATION—The invisible and harmless radiation emitted by a hot object. This radiation is converted into heat when it is absorbed.

INTERMITTENT IGNITION SYSTEM—Means of lighting the pilot or main burner without the use of a standing pilot, or main burner without the use of a standing pilot, by electronic spark or hot surface ignition. Also known as electronic ignition device.

JOINT COMPOUNDS—Non-hardening materials used on pipe threads to ensure a proper seal.

K-1 KEROSENE—A petroleum distillate, low sulfur fuel, is a complex mixture of paraffin’s, cycloparaffin’s, olefins, and aromatic hydrocarbons. May contain a trace amount of benzene (<0.01%). Contains a trace amount of sulfur (15-400 ppm). Kerosene has a minimum flash point of 100°F. Kerosene is used in space heaters, cook stoves, water heaters, and wick lamps.

K-1 KEROSENE (RED DYED) —Same as K-1 KEROSENE except it has been dyed red, by federal law, to designate it as exempt from certain highway taxes and is intended strictly for off road uses, such as heating fuel.

KEROSENE HEATER (portable)—Widely used portable heating appliance popular with consumers for zone heating needs as well as emergency heat during power outages.

KEROSENE HEATER (fan forced air/portable) —A portable kerosene heater that uses a fan to produce very high BTU output, commonly used in construction, or industrial applications where a large amount of heat is needed on a temporary basis. Not intended for use indoors or areas without proper ventilation.

KILOWATT—A unit of electrical power equal to 1000 watts.

KILOWATT HOUR—A measure of electricity defined as a unit of work or energy, measured as 1 kilowatt or power expended for one hour. One kilowatt is equivalent to 3,412 BTU.

LABELED—Equipment or material identified as having undergone approved inspection and compliance manufacturing and performance procedures.

LEAKAGE TESTING—Procedure to ensure that there is no uncontrolled flow of fuel gas in the gas piping system and or the appliance.

LIFTING FLAMES—An unstable burner condition in which flames rise above or blow off the burner port.

LIQUEFIED PETROLEUM GAS (LPG)—Colorless, odorless, and non-toxic gas separated from wet natural gas, light crude oil, and oil refinery gases. Composed predominantly of following hydrocarbons or mixtures thereof: propane, propylene, normal butane or isobutane and butylenes.

LIQUID PROPANE—Liquefied petroleum gas, available in cylinders, for home use.

LISTED—Included in a list published by a recognized testing laboratory or inspection agency, indicating that the equipment meets nationally recognized safety standards.

MANOMETER—Instrument used for measuring the pressure of gases.

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

MANUFACTURERS INSTALLATION INSTRUCTIONS—Instructions and recommendations for proper assembly, adjustment, and installation of listed equipment.

MILLIVOLT (MV)—Unit of electromotive force equal to one one-thousandth of a volt.

MULTI-METER—A device consisting of one or more meters used to measure two or more electrical quantities in an electrical circuit such as voltage, resistance, and current.

NATIONAL FUEL GAS CODE (ANSI Z23.1, NFPA 54)—A standard for the installation of gas appliances, piping and venting.

NATURAL GAS—Colorless, highly flammable gas found in porous geologic formations beneath the earth’s surface. A gaseous mixture of hydrocarbons, mainly methane used as a fuel for a variety of purposes ranging from the production of electricity, heating, etc.

NFPA—The National Fire Protection Association, 470 Atlantic Avenue, Boston, MA 02210. An independent, not-for-profit organization for fire safety.

ODORANT—Material added to natural gas or LPG in small concentrations to impart a detectably distinct odor. Usually mercaptan.

ONSPEX —A division of CSA International that provides consumer product evaluations, testing and inspection services worldwide.

ORIFICE—The opening in a cap, or other device whereby the flow of gas is limited and or controlled and through which the gas is discharged to either a pilot burner or main burner.

OTL CERTIFIED— “OTL” OMNI-Test Laboratories, Inc. (OMNI) is a full service hearth products testing, certification, and listing laboratory. OMNI's product testing programs are accredited by national and international accreditation bodies, including the American National Standards Institute (ANSI), the Standards Council of Canada (SCC), the International Accreditation Service, Inc. (IAS), and the U.S. Environmental Protection Agency (EPA).

OXYGEN DEPLETION DEVICE (ODS)—A device used to turn off the gas supply to a gas heating appliance should the oxygen level in the air drop below 18%. Often mistaken for just the pilot assembly, the complete system includes the pilot assembly, thermocouple, pilot mounting position, and gas valve assembly.

PFS CERTIFIED —PFS evaluates and certifies a broad range of products and structures. PFS is recognized by the International Accreditation Service, Inc. (IAS) as an ISO 17025 Testing Laboratory and as an ISO 17020 Inspection Agency for heating and gas appliances.

PTC CERAMIC—This material is named for its positive thermal coefficient of resistance (i.e., resistance increases upon heating). Most ceramics have a negative coefficient, whereas most metals have positive values. While metals do become slightly more resistant at higher temperatures, this class of ceramics, BARIUM TITANATE has a highly nonlinear thermal response, so that it becomes extremely resistant above a composition-dependent threshold temperature. This behavior causes the material to act as its own THERMOSTAT since current passes when it is cool, and does not when it is hot. Thin films of this material are used in automotive rear-window defrost heaters, and honeycomb-shaped elements are used in portable electric heaters.

PIEZO IGNITOR—A device which delivers an igniting spark by means of pressure on a crystal.

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

POWER FAILURE “CASCADE TYPE” —A cascade power failure is common in power grids when one of the elements fails (completely or partially) and shifts its load to nearby elements in the system. Those nearby elements are then pushed beyond their capacity so they become overloaded and shift their load onto other elements. Cascading failure is a common effect seen in high voltage systems, where a single point of failure (SPF) on a fully loaded or slightly overloaded system results in a sudden spike across all nodes of the system. This surge current can induce the already overloaded nodes into failure, setting off more overloads and thereby taking down the entire system in a very short time.

POWER GRID—A power or electrical grid is an interconnected network for delivering electricity from suppliers to consumers. It consists of three main components: 1) power stations that produce electricity from combustible fuels (coal, natural gas, biomass) or non-combustible fuels (wind, solar, nuclear, hydro power); 2) transmission lines that carry electricity from power plants to demand centers; and 3) transformers that reduce voltage so distribution lines carry power for final delivery.

POWER OUTAGE —Also known as a power cut, blackout, or power failure, is a short- or long-term loss of the electric power to an area. There are many causes of power failures in an electricity network. Examples of these causes include faults at power stations, damage to electric transmission lines, substations or other parts of the distribution system, a short circuit, overloading of electricity mains or even interference caused by solar flares.

PRESSURE REGULATOR—A device for controlling and maintaining a uniform outlet gas pressure. Service regulators reduce high street pressure of natural gas or reduce LPG storage tank pressure. Appliance regulators, usually part of the combination valve, reduce, adjust, and maintain constant pressure to be used in an appliance.

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

PRIMARY AIR—Combustion air directed to the firebox where the fuel is located; supports all stages of combustion.

PRIMARY COMBUSTION—The burning of fuel and some of the combustible gases, which takes place in that portion of the appliance where the fuel is.

PROPANE—A normally gaseous, colorless, odorless, straight chain hydrocarbon fuel containing more heat value than natural gas. It is extracted from natural gas or refinery gas streams.

PSI—Pounds of pressure per square inch.

RADIANT HEATER—A heating appliance whose main heat output is in the form of radiant energy. Radiant heaters are most effective when they are directed towards the desired area in need of heat.

RADIATION—Heat that moves out in waves from a central point and heats objects in its path. The closer you get to a source of radiant heat the more heat you will feel.

READY.GOV —Ready is a national public service advertising campaign designed to educate and empower Americans to prepare for and respond to emergencies including natural and man-made disasters. The goal of the campaign is to get the public involved and ultimately to increase the level of basic emergency preparedness across the nation.

SAFETY SHUTOFF—A device, usually powered by a thermocouple/thermopile, designed to shut off the gas supply to the pilot and or main burner if the source of ignition fails.

SALAMANDER HEATER—A slang term used to describe portable kerosene forced air heaters.

SEDIMENT TRAP—In gas piping, a tee device to intercept or hold solid foreign particles to prevent them from blocking valves or orifices. If not part of an appliance, must be installed as close to appliance inlet as possible.

SIPHON PUMP —A device used to transfer a liquid from one container to another with generally more ease and greater safety than attempting to transfer the liquid by pouring through a spout, etc. In the case of a manual siphon pump the flow is aided by squeezing a hand bulb to start the flow, while a battery siphon pump uses a small motor to aid in the flow and transfer of the liquid.

SOOT—Soft, black or brown, velvety deposit of carbon particles inside appliances, chimneys, and connectors. Soot originates in oxygen-poor flames.

SPECIFIC GRAVITY—The weight of one substance compared to the weight of another substance, both of equal volume and measured at the same temperature and pressure.

TEMPERATURE DIFFERENTIAL—The difference in temperature between two areas, such as inside and outside the house. (Example, if it is 90 degrees F. outside the house and 70 degrees F. inside the house, the temperature differential is 20 degrees F).

THERM—100,000 British Thermal Units (BTU’s).

THERMAL EFFICIENCY—Thermal efficiency is the measure of the efficiency and completeness of combustion of the fuel ONLY. Does not take into account the HEAT TRANSFER EFFICIENCY, which describes how effectively the heat is used after it is generated.

THERMAL MASS—The combination of an objects weight and its ability to absorb heat. Represents an objects capacity to act as a heat battery.

THERMOCOUPLE—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.

THERMOSTAT—An automatic device for regulating the temperature in a building by controlling the heating or cooling source or its distribution.

TORPEDO HEATER—A slang term used to describe portable kerosene forced air heaters.

TRASH CAN HEATER—A slang term used to describe liquid propane convection heaters.  Despite the negative tone on this name, these large silver heating giants remain a favorite of those needing to heat a large, well-ventilated area very quickly.

U.L. CERTIFIED—Underwriters Laboratories, Inc. 333 Pfingsten Road, Northbrook IL, 60062. An independent not-for-profit organization testing for public safety.

UNVENTED ROOM HEATER—category of unvented, self-contained, free standing, non recessed (except as noted) fuel gas burning appliance for furnishing warm air by gravity or fan without duct connection. Gas hearth appliances listed to ANSI Standard Z21.11.2 include Gas Fireplaces and Fireplace Inserts.

VENT FREE (GAS HEATER, APPLIANCE, ETC)—An appliance that is designed to operate efficiently without a chimney, flue, or vent. The term VENT FREE most commonly refers to products know as UNVENTED ROOM HEATERS and includes Gas appliances listed to ANSI Standard Z21.11.2 such as Gas Heaters, Stoves, Logs, Fireplaces, and Gas Fireplace Inserts.

WATER COLUMN (WC)—Measurement in inches of pressure of gas. 28 inches WC equals one PSI.

WATER MANOMETER—A device used to measure gas pressures in inches of water column.

WICK—A textile product made of cotton and fiberglass, used to draw fuel from a fuel tank to the wick’s top surface where combustion takes place. Most commonly used in kerosene heaters, lamps, lanterns and tiki torches.

ZERO CLEARANCE FIREPLACE—A factory built fireplace that is constructed so that it can be placed safely close to combustible materials.

ZONE HEATING—The practice of reducing the temperature setting of a home’s central heating system, closing off unused rooms and spaces and only heating occupied spaces with smaller space heaters, usually kerosene, gas or electric powered.