Accessible (for Inspections) - Capable of being exposed for inspection, maintenance, or repair without damage to the chimney or building structure or finish, but which may require the removal of doors, panels, or coverings using commonly available tools.

ACID CLEANING - The process of cleaning the interior surfaces of steam generating units by filling the unit with dilute acid accompanied by an inhibitor to prevent corrosion, and subsequently draining, washing and neutralizing the acid by a further wash of alkaline water.

ACIDITY - Represents the amount of free carbon dioxide, mineral acids and salts (especially sulphates of iron and aluminum) which hydrolyze to give hydrogen ions in water and is reported as milliequivalents per liter of acid, or ppm acidity as calcium carbonate, or pH the measure of hydrogen ions concentration.

Aggregate - Ingredients of concrete; gravel and sand, mixed with portland cement.

AIR - The mixture of oxygen, nitrogen, and other gases, which with varying amounts of water vapor, formsAccessible (for Inspections). Capable of being exposed for inspection, maintenance, or repair without damage to the chimney or building structure or finish, but which may require the removal of doors, panels, or coverings using commonly available tools. the atmosphere of the earth.

AIR DEFICIENCY - Insufficient air, in an air-fuel mixture, to supply the oxygen required for complete oxidation of the fuel.

AIR INFILTRATION - The leakage of air into a setting or duct

Anchor Bolts - Bolts used to secure a wooden sill to a masonry foundation.

Appliance - Utilization equipment, normally built in standardized sizes or types, that is installed or connected as a unit to perform one or more functions such as clothes washing, air conditioning, food mixing, cooking, heating, or refrigeration.

Appliance Casing (or jacket) -An enclosure forming the outside of the appliance.

Appliance Categories - See Gas Appliance Categories.

Appliance Flue - The flue passage within an appliance.

Asbestos Shingles - Fireproof roof or siding material made of portland cement and asbestos.

ASH - The incombustible inorganic matter in the fuel.

Ash - The solid residue that remains after combustion is complete.

ASH PIT - A pit or hopper located below a furnace where refuse is accumulated and from which refuse is removed at intervals.

Ash Receptacle Door - A door below the grade level providing access to the ash receptacle.

Attic -Type Heating Appliance. A heating appliance designed specifically for installation in an attic or in a space with low headroom that normally is unoccupied.

Automatic Electric Igniter - A device for fuel burners designed to utilize electric energy for ignition of a fuel-air mixture at the burner.

Automatically Lighted Fuel-Burning Appliance - A fuel-burning appliance in which fuel to the main burner is normally turned on and ignited automatically.

Automatically Operated Damper - A damper operated by an automatic control.

Baffle - An object placed in an appliance to change the direction of, or to retard, the flow of air, air-fuel mxtures, or flue gases.

Barometric Draft Regulator - A device built into a fuel-burning appliance, or made a part of a chimney connector or vent connector, that functions to reduce excessive draft through an appliance to a desired value by admitting ambient air into the appliance chimney, chimney connector, vent, or vent connector.

Boiler - A vessel in which water is heated, steam is generated, or steam is superheated, or in which any combination thereof takes place by the application of heat from combustible fuels, in a self-contained or attached furnace.

Bond - Where referring to bricklaying and masonry chimneys, that connection between brick, stone, or other masonry units formed by lapping them upon one another in carrying up the work, thereby forming an inseparable mass.

Breeching - The conduit conveying flue gas from the appliance to the chimney.

Btu - Abbreviation for British thermal unit. The quantity of heat needed to raise the temperature of 1 pound of water 1F.

Building Code - A set of rules and regulations established by local government, which determines the standards for procedures and materials in construction.

Building Heating Appliance - A fuel-burning or electric boiler operating at a gauge pressure not over 50 psig (345 kPa), a central furnace, or a heater intended primarily for heating spaces having a volume exceeding 25,000 ft3 (708m3).

Built-up Roof - A flat or low pitched roof of three or more layers of tar-saturated felt or jute; the surface is finished with gravel or crushed slag.

C - Carbon element, the principal combustible constituent of all fuels.

Caulk - To fill seams and joints with a flexible, durable substance to make them watertight and airtight.

Central Warm-Air, Forced-Air, Attic-Type Furnace - A forced-air-type-furnace designed specifically for installation in an attic or in a space with low headroom that is normally occupied.

Central Warm-Air, Forced-Air, Down flow-Type Furnace - A forced-air-type furnace designed specifically in a vertical path, discharging air at or near the bottom of the furnace.

Central Warm-Air, Force-Air, Horizontal-Type Furnace - A forced-air-type furnace designed with airflow through the furnace essentially in a horizontal path.

Central Warm-Air, Forced-Air-Type-Furnace - A central furnace equipped with a blower that provides the primary means for the circulation of air.

Central Warm-Air, Forced-Air, Upflow-Type Furnace - A forced-air-type- furnace designed with airflow essentially in a vertical path, discharging air at or near the top of the furnace.

Central Warm-Air Furnace - A self-contained indirect-fired or electrically heated appliance designed to supply heated air through ducts to spaces remote from or adjacent to the appliance location.

Central Warm-Air, Gravity-Type Furnace - A central furnace depending primarily on circulation of air by gravity.

Central Warm-Air, Gravity-Type Furnace with Booster Fan - A central furnace equipped with a fan as an integral part of its construction and operable on gravity systems only. The fan is used only to overcome the internal resistance to airflow.

Central Warm-Air,Gravity-Type Furnace with Integral Fan - A central furnace equipped with a fan as an integral part of its construction and operable on gravity systems only. The fan is used to overcome the internal resistance to airflow.

CHIMNEY - flues, or channels, through which smoke is expelled from a fireplace or furnace.

Chimney - A structure containing one or more vertical or nearly vertical passageways for conveying flue gases to the outside atmosphere.

Chimney Cap - A protective covering or housing for the top of a chimney intended to prevent the entry of rain, snow, animals, and birds, to prevent downdrafts.

Chimney Connector - The pipe that connects a fuel-burning appliance to a chimney.

Chimney Connector-Type Heat Reclaimer - A heat exchanger intended to be installed in a chimney connector between a heating appliance and the chimney to transfer heat from the flue gases through metal to air or water.

Chimney Flue - The passage in a chimney for conveying the flue gases to the outside atmosphere.

Chimney Flue Base (Base of Flue) - The lowest point of a flue, within a chimney.

Chimney pot - A cylindrical pipe of brick, terra-cotta, or metal placed on the top of a chimney to improve the draft to draw away noxious fumes from coal-burning fireplaces

CHIMNEY SWEEP - A worker employed to clean soot from chimneys.

Circulating Room Heater - A room heater with an outer jacket surrounding the heat exchanger, arranged with openings at top and bottom so that air circulates between the heat exchanger and the outer jacket. Room heaters that have openings in an outer jacket to allow some direct radiation
From the heat exchanger are classified as a radiant type.

CIRCULATION - The movement of water and steam within a steam generating unit.

CLEANOUT DOOR - A door placed so that accumulated refuse may be removed room a boiler setting.

Cleanout Opening - An opening or hole in a chimney, usually located near its base, designed to allow access to the flue for purposes of removing ash, creosote, soot, and other extraneous matter that becomes trapped.

Clearance - The distance between a heat-producing appliance, chimney, chimney connector, vent, vent connector, or plenum and other surfaces.

Clothes Dryer - A device used to dry wt laundry by means of heat derived from the combustion of fuel or from electric heating elements.

CO - Carbon monoxide.

CO2 - Carbon dioxide.

Combination-Fuel Boiler - A single boiler unit designed to burn more than one type of fuel (gas, oil, or solid), either separately or simultaneously using either separate or common combustion chambers and flues.

Combination-Fuel Furnace - A single furnace unit designed to burn more than one type of fuel (gas, oil or solid), either separately or simultaneously, using either separate or common combustion chambers and flues.

Combination Room/Heater/Fireplace Stove - A chimney-connected, solid fuel-burning room heater that is designed to be operated with the fire chamber either open or closed.

Combustion - A chemical process of oxidation that occurs at a rate fast enough to produce heat and usually light in the form of either a glow or flame.

Combustion Air - The air necessary to provide for the complete combustion of fuel and usually consisting of primary air, secondary air, and excess air.

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, or whether plastered or unplastered.

Combustion Products - Constituents resulting from the combustion of a fuel with the oxygen of the air, including the inerts but excluding excess air.

Common Brick - The least expensive red brick used for construction and lacking the attractive texture and water-resistant qualities of tapestry or face brick.

COMBUSTIBLES - The heat producing constituents of a fuel.

COMBUSTION - The rapid chemical combination of oxygen with the combustible elements of a fuel resulting in the release of heat.

COMBUSTION AIR - Air used in the combustion process. Air contains oxygen which is required to combust fuel.

COMBUSTION CHAMBER - See Furnace.

COMPLETE COMBUSTION - The complete oxidation of all the combustible constituents of a fuel.

Condensation - Droplets of water sometimes appearing as frost on inside surfaces of exterior walls or windows in cold weather, and caused by excessive moisture-laden air in poorly ventilated buildings.

Confined Space - A space whose volume is less than 50ft3/1000 Btu/hr (1.42 m3/293W) of the aggregate input rating of all appliances installed in that space.

Cooking Appliance (Floor-Mounted Restaurant-Type) - A range, oven, broiler, or other miscellaneous cooking appliance designated for use in hotel and restaurant kitchens and for mounting on the floor.

Corrosion - The gradual destruction of a substance due to a chemical reaction.

Corbel - Units of masonry projecting from or projecting upward and outward from the face of a wall or chimney in courses to form a support or ledge for a beam, rafter, or other member.

Counter Appliance (Gas) - Appliances such as gas-operated coffee brewers and coffee urns and any appurtenant water-heating equipment, food and dish warmers, hot plates, and griddles.

Damper - A metal device to regulate draft in the flue of a boiler, furnace or fireplace.

Damper - A valve or plate for controlling draft or the flow of gases, including air.

Decorative Shroud - A partial enclosure for aesthetic purposes that is installed at the termination of a venting system that surrounds or conceals the chimney or vent cap.

Dew Point - The temperature at which water vapor in the air begins to condense into droplets.

Dilution Air - The air that enters the relief opening of a draft hood or draft diverter, or the air that enters another opening in an appliance flue or venting system.

Dilution Flue - A passage designed to effect the dilution of flue gses with air before discharge from an appliance.

Direct Vent appliance (Sealed Combustion System Appliance) - A system consisting of an appliance, combustion air and flue gas connections between the appliance and the outside atmosphere, and a vent cap supplied by the manufacturer, and constructed so that all air for combustion is obtained from the outside atmosphere and all flue gases are discharged to the outside atmosphere.

DRAFT - The difference between atmospheric pressure and some lower pressure existing in the furnace stack or gas passages of a steam generating unit.

Draft - The pressure differential that causes the flow of air or gases through a chimney, gas vent, or venting system.

Draft Hood - A device built into an aplliance, or made a part of the vent connector from an appliance, that is designed to (1) provide for the ready escape of the flue gases from the appliance in the event of no draft, backdraft, or stoppage beyond the draft hood, (2) prevent a backdraft from entering the appliance, and (3) neutralize the effect of stack action of the chimney or gas vent upon the operation of the appliance.

DUCT - A passage for air or gas flow.

Duct Furnace - A central furnace designed for installation in a duct of an air distribution system to supply warm air for heating and that depends on a blower not furnished as part of the furnace for air circulation.

EFFICIENCY - The ratio of output to input.

Engineered Venting or Chimney System - A system that has been sized and configuered in accordance with approved engineering methods.

EXCESS AIR - Air supplied for combustion in excess of that theoretically required for complete oxidation.

Efflorescence - A growth of salt crystals on a surface caused by evaporation of salt-laden water

Facebrick - A type of brick made of selected clays and often textured which is highly water-resistant. Also called tapestry brick.

Factory-Built Appliance - A manufactured appliance furnished by the manufacturer as a single assembly or as a package set of subassemblies or parts, and including all the essential components necessary for it to function normally where installed as intended.

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

Factory-Built, Building Heating Appliance Type Chimney - A heating appliance chimney suitable for continuous use at 1000F (538C), composed of listed, factory-built components, designed for open, nonenclosed use at specified minimum clearances to combustibles, and assembled in accordance with the terms of the listing to form the completed chimney.

Factory-Built, Medium-Heat Appliance Type Chimney - A chimney used with appliances that produce maximum flue gas temperatures of 1800F (982C), composed of listed, factory-built components, suitable for open, nonenclosed use a specified minimum clearances to combustibles, and assembled in accordance with the terms of the listing to form the completed chimney.

Factory-Built, Positive Pressure Capable Chimney - A residential type or building heating appliance chimney, or both, listed for use in positive internal pressure applications.

Factory-Built, Residential Type and Building Heating Appliance Type Chimney - A chimney suitable for use at 1000F (538C) which complies with the 10 minute 1700F Temperature test of UL 103, Factory-Built Chimneys for Residential Type and Building Heating Appliance, and is composed of listed, factory built components that might be fully enclosed in combustible, residential type construction, and that is assembled in accordance with the terms of the listing to form a completed chimney.

Factory-Built, Residential Type and/or Building Heating Appliance Type Chimney-Type HT - A residential type and building heating appliance chimney suitable for use at 1000F (538C) which complies with the optional 10 minute 2100F temperature test of UL 103, factory-Built Chimneys for Residential Type and Building Heating Appliance. Such chimneys are labeled as Type HT and are required for certain solid fuel-fired applications.

Factory-Built, 1400F Type Chimney - A chimney suitable for continuous use at 1400F (760C), composed of listed, factory-built components, intended for open, nonenclosed use at specified minimum clearances to combustibles and for use in noncombustible locations, and assembled in accordance with the terms of the listing to form the completed chimney.

Fan - A blower or exhauster assembly comprising blades or runners and housing or casings.

FLAME - A luminous body of burning gas or vapor.

FLAMMABILITY - Susceptibility to combustion.

FLUE - A passage for products of combustion.

Flue Collar - That portion of an appliance designed for attachment of a chimney or vent connector or a draft hood.

FLUE GAS - The gaseous product of combustion in the flue to the stack.

Flue Gases - Combustion products from fuel-burning appliances along with excess air.

Flue Gas Damper - A damper located on the downstream side of the combustion chamber of a fuel-burning appliance, usually in a flue passage of the appliance or in the chimney or vent connector.

Firebrick - A brick made of special fire clay to resist high heat.

Fire Clay - Material that can withstand very high temperatures without softening or fusing and to line chimney flues and fire chambers of boilers and furnaces.

Fireplace - A hearth, fire chamber, or similarly prepared area and a chimney.

Fireplace Accessories - Accessories intended for field installation into or attachment to existing masonry fireplaces. These include such items as heat exhangers, door assembies, tubular grates, and blowers.

Fireplace Insert - A factory-built, field installed product consisting of a firebox assembly designed to be installed within or partialy within the fire chamber of a fireplace that uses the fireplace flue to vent the products of combustion.

Fireplace Stove - A freestanding, chimney-connected, solid fuel-burning appliance that is designed to be operated with the fire chamber either open or closed.

Firestop - Any solid object used to block airways between walls to prevent smoke and fire from spreading.

FLAME - A luminous body of burning gas or vapor.

Flame Spread Rating - A relative measurement of the surface burning characteristics of building materials when tested in accordance with NFPA 255, Standard Method of Test of Surface Burning Characterstics of Building Materials.

FLAMMABILITY - Susceptibility to combustion.

Flashing - Sheet metal or other material used around chimneys, dormers, windows and joints where angles meet to protect a structure from water seepage.

Floor Protector - A noncombustilble sufacing applied to the floor area undrneath and extending in front, to the sides, and to the rear of a heat-producing appliance.

Flue - An enclosed chimney passage through which gas and smoke rise to open air.

Flue - The genral term for a passage in a chimney for conveying the flue gases to the outside atmosphere.

Flue Lining - Round or square fire clay or terra-cotta pipe made in two foot lengths which prevents smoke and hot gases from escaping through the wall of the chimney into the house.

FUEL - A substance containing combustible used for generating heat.

Gas Vent - A passageway composed of listed factory-built components assembled in accordance with the terms of listing for conveying vent gases from gas appliances or their vent connectors to the outside atmosphere.

Hardwood - Lumber from trees that shed their broad leaves in the fall. The term hardwood or softwood is not an accurate index of relative hardness. Some softwoods such as southern yellow pine or Douglas fir are much harder than the hardwoods poplar or basswood. See softwood.

Header - Where referring to chimneys, a beam set at right angles to floor or roof joists to provide suport and framing around the opening.

Hearth - The floor of a fireplace, including the part that extends into the room constructed of tile, brick or stone.

Hearth - The floor area within the fire chamber of a fierplace or a fireplace stove.

Hearth Extension - The noncombustible surfacing applied to the floor area extending in front of and at the sides of the hearth opening of a fireplace or a fireplace stove; also where applied to the floor area beneath a fireplace stove or beneath an elevated overhanging fireplace hearth.

Heat Exchanger - A chamber in which heat resulting directly from the combustion of fuel, or heat from a medium such as air, water, or steam, is transferred through the walls of the chamber to air passing through the exchanger; or a chamber in which heat from electric resistors is transferred to the air.

Heat-Producing Appliance - An appliance that produces heat by utilizing electric energy or by burning fuel.

High-Pressure Boiler - A boiler for generating steam at gauge pressures in excess of 15psi (103 kPa) or for heating water to a temperature in excess of 250F (121C) or at a gauge pressure in excess of 160psi (1103 kPa).

Hot Water Supply Boiler - A boiler used to heat water for purposes other than space heating.

IGNITION - The initiation of combustion.

IGNITION TEMPERATURE - Lowest temperature of a fuel at which combustion becomes self-sustaining.

INCOMPLETE COMBUSTION - The partial oxidation of the combustible constituents of a fuel.

INHIBITOR - A substance which selectively retards a chemical action.

Jamb - The upright piece forming the side of an opening as of a door, window or fireplace.

K Factor - The rate of speed at which heat, measured in BTU's will pass through the material of an exterior wall.

Kiln-Dried - A method of seasoning lumber in ovens which is a faster process than air drying.

LEAKAGE - The uncontrolled quantity of fluid which enters or leaves through the enclosure of air or gas passages.

LINING - The material used on the furnace side of a furnace wall. It is usually of high grade refractory tile or brick or plastic refractory material.

Listed - Equipment materials, or services included in a list published by an organization that is acceptable to the authority having jurisdiction and concerned with evaluation of products or services, that maintains periodic inspection of production of listed equipment or materials or periodic evaluation of services, and whose listing states that either the equipment, material, or service meets appropriate designated standards or has been tested and found suitable for a specified purpose.

Low-Pressure Boiler - A boiler for generating steam at gauge pressures not in excess of 15 psi (103 kPa) or for furnishing water at a maximum temperature of 250F (121C) at a maximum gauge pressure of 160 psi (1103 kPa).

Manually Operated Damper - An adjustable damper manually set and locked in the desired position.

Masonry - Anything built of materials such as concrete, stone, brick or tile.

Masonry Chimney - A field-constructed chimney of solid masonry units, bricks, stones, listed masonry chimney units, or reinforced Portland cement concrete that is lined with suitable chimney flue liners and built in accordance with the provisions of Chapter 4 of this standard.

Masonry fireplace - A hearth and fire chamber of solid masonry units, such as bricks, stones, listed masonry units, or reinforced concrete, provided with a suitable chimney.

Masonry Fireplace Litel - The horizontal, noncombustible member, usually of masonry or steel, spanning the opening of a masonry fireplace to support the load above.

Mechanical Draft - Draft produced by a fan or an air or steam jet. When a fan is located so as to push the flue gases through the chimney or vent, the draft is forced. When the fan is located so as to pull the flue gases through the chimney or vent, the draft is induced.

MOISTURE - Water in the liquid or vapor phase.

Moisture Barrier - A waterproof material placed against the inner side of exterior walls to prevent moisture form forming on the wood.

Mortar - A mixture of cement, sand and water used to bond bricks and stone.

Natural Draft - Draft produced by the difference in the weight of a column of flue gases within a chimney or vent and a corresponding column of air of equal dimension outside the chimney or vent.

NATURAL GAS - Gaseous fuel occurring in nature.

Noncombustible Material - A material that, in the form in which it is used and under the conditions anticipated, will not ignite, burn, support combustion, or release flammable vapors when subjected to fire or heat. Materials that are reported as passing ASTM E. 136, Standard Test Method for Behavior of Meterials in a Vertical Tube Furnace at 750 C, shall be considered noncombustible materials. (220:2-1).

Nonresidential Appliance, 1400F - A commercial industrial, or institutional appliance needing a chimney capable of withstanding a continuous flue gas temperature not exceeding 1400F (760C)

Nonresidential, High-Heat Appliance - A commercial, industrial, or institutional appliance needing a chimney capable of withstanding a continuous flue gas temperature exceeding 1800F (982C).

Nonresidential, Low-Heat Appliance - A commercial, industrial, or institutional appliance needing a chimney capable of withstanding a continuous flue gas temperature not exceeding 1000F (538C).

Nonresidential, Medium-Heat Appliance - A commercial, industrial, or institutional appliance needing a chimney capable of withstanding a continuous flue gas temperature not exceeding 1800F (982C).

Non-Accessible, Concealed (for Inspections) - Not capable of being exposed for inspection, maintenance, or repairwithout damage to the chimney or building structure or finish, or without the use of special tools.

Pellet Fuel - A solid processed fuel of specified size and composition system at a controlled rate.

Pellet Fuel-Burning Appliance - A closed combustion pellet vent or chimney-connected solid pellet fuel-burning appliance incorporating a fuel-feed control mechanism.

Pellet Vent - A venting system composed of listed, factory-built components assembled in accordance with the manufacturer’s instructions for conveying flue gases from a listed pellet fuel-burning appliance to the outside atmosphere.

PERFECT COMBUSTION - The complete oxidation of all the combustible constituents of a fuel, utilizing all the oxygen supplied.

Pier - A masonry pillar used to support other structural members.

Qualified Agency - Any individual, firm, corporation, or company that, either in person or through a representative, is engaged in and is responsible for the connection, venting, installation, inspection, repair, or servicing of heat-producing appliances and who is experienced in such work, is familiar with all precautions required, and has complied with all the requirements of the AHJ.

R Value - A grading standard for insulating materials. It stands for "resistance to heat flow" and is stamped on most good brands of insulation material. The higher the R value the better.

Radiant Room Heater - A room heater designed to transfer heat primarily by direct radiation.

Readily Accessible (for Inspections) - Exposed, or capable of being exposed of operation, inspection, maintenance, or repair without the use of tools to open or remove doors, panels, or coverings.

Register - In warm-air heating, a grill that allows the heated air to pass into different rooms.

RELATIVE HUMIDITY - The ratio of the mass of water vapor present in a unit volume of gas to the maximum possible mass of water vapor in unit volume of the same gas at the same temperature and pressure.

Residential Type Heating Appliance - Fuel-burning and electric heating appliances, not including high-pressure steam boilers, for heating building spaces having a volume of not more than 25,000 ft3 (708m3) and other heat-producing appliances of the type mainly used in residences but that might be used in other buildings, such as cooking stoves and ranges, clothes dryers, fireplace stoves, domestic incinerators, laundry stoves, water heaters and heat pumps.

Roof Jack - A factory-built assembly for conveying flue gases through a roof and that includes a flue gas passageway, an insulating means, flashing, and a cap.

Room Heater - A heating appliance intended for installation in the space being heated and not intended for duct connection.

Room Large In Comparison with the size of the Appliance - A room having a volume equal to at lest 12 times the total volume of a furnace and at least 16 times the total volume of a boiler. The total volume of the furnace or boiler is determined from the exterior dimensions and is to include a fan compartment and burner vestibule, where used. Where the actual ceiling height of a room is greater than 8 ft (2.44 m), the volume of the room is to be figured on the basis of a ceiling height of 8 feet (2.44 m).

SMOKE - Small gas borne particles of carbon or soot, less than 1 micron in size, resulting from incomplete combustion of carbonaceous materials and of sufficient number to be observable.

Smoke Chamber - The transitional area from the damper opening to the beginning of the flue liner in a fireplace system.

Smoke Developed Rating - The smoke developed rating of materials as determined by NFPA 255, Standard Method of Test OF Surface Burning Characteristics of Building Materials, ASTM E. 84, Standard Test Method for Surface Burning Characteristics of Building Materials; and UL 723, Standard for Safety Test for Surface Burning Characteristics of Building Materials.

Smoke Test - A procedure for ascertaining the tightness of a chimney and for detecting any cracks in a masonry chimney flue or deterioration or breaks in the integrity of a metal chimney flue, and that involves igniting a smoke bomb or building a smoky fire in a fireplace or solid fuel-burning appliance, covering the chimney termination, and checking for smoke escapage through the chimney walls.

Shingles - Small rectangular or square pieces of building material laid in overlapping rows on the roof or walls of a house.

Softwood - Cone-bearing, evergreen trees which except for the cypress and larch do not shed their needle-like leaves. See Hardwood.

Solid Fuel - Wood, coal, and other similar organic materials and any combination of them.

Solid Fuel-Burning Appliance - A chimney-connected device that burns solid fuel designed for purposes of heating, cooking, or both.

Solid Fuel Room Heater - A chimney-connected, solid fuel-burning rom heater that is designed to be operated with the fire chamber closed.

Solid Masonry Construction - A bonded assembly of stones or solid masonry units.

Solid Masonry Unit - A masonry unit whose net cross-sectional area in every plane parallel to the bearing surface is 75 percent or more of its gross cross-sectional area measured in the same plane.

Spark Arresters - Screening material or a screening device attached to a chimney termination to prevent the passage of sparks and brands to the outside atmosphere.

Special Gas Vent - A gas vent for venting listed Category II, III , and IV gas appliances.

Splay - Wash.

STACK - A vertical conduit, which due to the difference in density between internal and external gases, creates a draft at its base.

STAGNATION - The condition of being free from movement or lacking circulation.

Steel Fireplace Unit - A unit consisting of a steel firebox and an air chamber adjacent to the sides and rear of the firebox, used to construct a masonry fireplace. The unit usually has ducts to circulate air to and heated air from the air chamber to the

Supplementary Boiler - A boiler, designed to burn one type of fuel (gass, oil, or solid), that is intended for supplementing a boiler burning another type of fuel (gass, oil, or solid) by means of a common heat transfer medium.

Supplementary Furnace - A furnace designed to burn one type of fuel (gas, oil, or solid) that is intended for supplementing a central warm-air furnace burning another type of fuel (gas, oil, or solid) by means of a common warm-air supply plenum.

Thimble - A fixed or removable ring, tube, or lining usually located in the hole where the chimney connector or vent connector passes through a wall or enters a chimney or vent.

Trimmer - Where referring to chimneys, the longer floor or roof framing member around a rectangular opening into which the end of a header is joined.

Type B Gas Vent - A vertical or nearly vertical gas vent of venting listed for use with Type B gas vents.

Type BW Gas Vent - A vertical or nearly vertical gas vent for venting listed gas-fired vented wall furnaces.

Type L Vent - A vertical or nearly vertical vent composed of listed factory-built components assembled in accordance with the terms of listing for conveying flue gases from oil and gas appliances or their vent connectors to the outside atmosphere.

Type 1 Clothes Dryer - A factory-built, mass-produced dryer, primarily used in a family living environment. It might or might not be coin-operated for public use and usually is the smallest unit both physically and in function.

Type 2 Clothes Dryer - A factory-built, mass-produced dryer used in a commercial business. It might or might not be operated by the public or a fired attendant. It might or might not be coin-operated and is not designed for use in an individual family living environment. It can be small, medium, or large in size.

Unit Heater - A self-contained heating appliance that might or might not include an integral fan for circulating air and that can be of the floor-mounted or suspended type that is intended for the heating of the space in which it is installed. A unit heater can be an indirect-fired fuel-burning appliance or might utilize steam, hot water, or electricity.

Unlisted Metal (Smokestack) Chimney - A manufactured or filed-constructed chimney intended only for non-residential applications having one or more metal walls, or made of metal with a refractory lining, and that is capable of withstanding the flue gas conditions of its use.

Vent - A flue gas conveying system intended for use only with certain gas, liquid, or pellet fuel-fired appliances that do not produce flue gas outlet temperatures higher than a value specified in the listing vent standards.

Vent Cap - A protective covering or housing attached to the vent termination, intended for preventing downdrafts and the entry of rain, snow, and animals.

Vent Connector - The pipe that connects a fuel-burning appliance to a gas vent or Type L vent.

Vent Gases - Products of combustion from fuel-burning appliances along with excess air, plus any dilution air in the venting system above a draft hood or draft regulator.

Vented Aplliance - An indirect-fired appliance provided with a flue collar to accommodate a venting system for conveying flue gases to the outside atmosphere.

Venting - Removal of combustion products as well as noxious or toxic fumes to the outside atmosphere.

Venting System (Flue Gases) - A continouous, open pasageway from the flue collar or draft hood of a fuel-burning appliance to the outside atmosphere for the purpose of removing flue gases.

Wall Protector (Shield) - Noncombustible surfacing applied to a wall area for the purpose of reducing the clearance between the wall and a heat producing appliance.

Wash - A slight slope or beveled edge on the top surface of a chimney designed to shed water away from the flue liner.

Water Heater - A fuel-burning appliance for heating water to a temperature not more than 200F (93C)

Weephole - A small opening in the lower part of a retaining wall to allow drainage of excess water.

Wythe - Where referring to masonry chimneys, a course, a thickness, or a continuous vertical section of masonry separating flues in a chimney.

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