There are many specialized terms utilized by the structural fire community. Find out what a particular term means by looking it up in the glossary.



Any federal, state or county government organization participating with jurisdictional responsibilities.

Aid Agreement

A formal agreement between two or more agencies where on party assists another party. It is used primarily for areas in which a Park depends on assistance for fire protection from a local community


A visual or audio warning of danger.

Alarm Signal

A signal indicating an emergency that requires immeditae action, such as a signal indicative of fire.


A system, condition, arrangement, material, or equipment submitted for approval to Authority Having Jurisdiction.

Annual Fire Safety Inspection

A yearly fire inspection conducted by a qualified individual either in the private or public sector to identify fire code deficiencies.


Acceptable to the Authority Having Jurisdiction


The generic name for a high-strength, flame-resistant synthetic fabric used in the shirts and pants of firefighters. Nomex, a brand name for aramid fabric, is the term commonly used by firefighters.


Direction toward which a slope faces.


Real or Personal Property or a component thereof.

Asset Damage

A condition deficiency resulting from damage caused by deterioration and other unforeseen impacts to the physical condition of the assor, or any form of deferred maintenance, neglect, or detrimental action by employees, agents, contractors, visitors, animals, and insects.

Asset Wear

The progressive deterioration (not coaused by deferred maintenance) of construction materials, hardware, window and door systems, switches, floor planking, pavement and or other components.

Authority Having Jurisdiction (AHJ)

The organization, office, or individual responsible for approving equipment, materials, installation, or procedure.

Automatic Fire Extinguishing System

Any system that is designed and installed to detect a fire and subsequently discharge an extinguishing agent without human activation or direction.



A fire set along the inner edge of a fireline to consume the fuel in the path of a wildland fire and/or change the direction of force of the fire's convection column.

Backing Fire

Fire that is moving into the wind.

See also Heading Fire and Flanking Fire


Old terminology used to indicate a Park maintained firefighting force.

See also Structural Fire Engine Company


Any structure used or intended for supporting or sheltering any use or occupancy.

Building Construction

Buildings or parts of buildings classified in a specific occupancy group because of their use limited to specified types of construction.

Burn Out

Setting fire inside a control line to widen it or consume fuel between the edge of the fire and the control line.


Central Station Fire Alarm System

A system or group of systems in which the operations of circuits and devices are transmitted automatically to, recorded in, maintained by, and supervised from a listed central station that has competent and experienced servers and operators who, upon receipt of a signal, tack such action as required by National Fire Protection Association Code 72 (Fire Alarm Code). Such service is to be controlled and operated by a person, firm, or corporation whose business is the furnishing, maintaining, or monitoring of supervised fire alarm systems.

Certified Structural Firefighter

A peson who has graduated from the NPS firefighter course or equivalent and who has been issued a certificate that states demonstration of the knowledge and skills necessary to function in the roll of a structural firefighter.

Class A Fire

Ordinary combustable materials, such as wood, cloth, paper, rubber, and many plastics on fire.

Class B Fire

Flammable liquids, combustable liquids, petroleum greases, tars, oils, oil-based paints, solvents, lacquers, alcohols, and flammable gases on fire.

Class C Fire

Engergized electrical equipment on fire.

Class D Fire

Combustible metals, such as magnesium, titanium, zerconium, sodium, lithium, and potassium on fire.

Class K Fires

Cooking appliances that involve combustible cooking media (vegetable or animal oils and fats) on fire.


A standard that is an extensive compilation of provisions covering broad subject matter or that is sutibale for adoption into law independently of other codes and standards.


A material that, in the form in which it is used and under the conditions anticipated, will ignite and burn; a material that does not meet the definition of noncombustible or limited-combustible.


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.


A portion of an asset.

Component Renewal

The planned replacement of a component that will reach the end of its serviceable life.

Condition Deficiency

A condition that may impact or reduce the serviceability, life, or economic value of an asset.

Condition Standards

The criteria used to form the basis for rating the condition of an asset or component of an asset.

Cooperating Agency

An agency supplying assistance other than direct suppression, rescue, support or service functions to the incident control effort; e.g., Red Cross, law enforcement agency, telephone company, etc.


Defensible Space

An area either natural or manmade where material capable of causing a fire to spread has been treated, cleared, reduced, or changed to act as a barrier between an advancing wildland fire and the loss of life, property, or resources. In practice, "defensible space" is defined as an area of a minimum of 30 feet around a structure that is cleared of flammable brush or vegetation.

Direct Attack

Any treatment of burning fuel, such as by wetting, smothering or chemically quenching the fire or by physically separating burning from unburned fuel.


The implementation of a command decision to move a resource or resources from one place to another.

Dispatch Center

A facility from which resources are directly assigned to an incident.


A person employed who receives reports of discovery and status of fires, confirms their locations, takes action promptly to provide people and equipment likely to be needed for control in first attack, and sends them to the proper place.


Any tracked vehicle with a front-mounted blade used for exposing mineral soil.

Dozer Line

Fire line constructed by the front blade of a dozer.

Drip Torch

Hand-held device for igniting fires by dripping flaming liquid fuel on the materials to be burned; consists of a fuel fount, burner arm and igniter. Fuel used is generally a mixture of diesel and gasoline.



Any ground vehicle providing specified levels of pumping, water and hose capacity.

Engine Crew

Firefighters assigned to an engine. The Fireline Handbook defines the minimum crew makeup by engine type.

Equilibrium Moisture Content

Moisture content that a fuel particle will attain if exposed for an infinite period in an environment of specified constant temperature and humidity. When a fuel particle reaches equilibrium moisture content, net exchange of moisture between it and the environment is zero.


Fire Triangle

Instructional aid in which the sides of a triangle are used to represent the three factors (oxygen, heat, fuel) necessary for combustion and flame production; removal of any of the three factors causes flame production to cease.

Firefighting Resources

All people and major items of equipment that can, or potentially can, be assigned to fires.


Water in which a surfactant has been added at the pump. Foam insulates fuels against heat, increases the penetration of water into fuels and decreases evaporation.


Hazard Reduction

Any treatment of a hazard that reduces the threat of ignition and fire intensity or rate of spread.



Under high pressure and stable air conditions, warm air may cap cooler air, forming an inversion that traps smoke in valley bottoms, particularly at night.


Ladder Fuels

Fuels which provide vertical continuity between strata, thereby allowing fire to carry from surface fuels into the crowns of trees or shrubs with relative ease. They help initiate and assure the continuation of crowning.


Mutual Aid Agreement

Written agreement between agencies and/or jurisdictions in which they agree to assist one another upon request, by furnishing personnel and equipment.


Pack Test

Used to determine the aerobic capacity of fire suppression and support personnel and assign physical fitness scores. The test consists of walking a specified distance, with or without a weighted pack, in a predetermined period of time, with altitude corrections.

Personnel Protective Equipment (PPE)

All firefighting personnel must be equipped with proper equipment and clothing in order to mitigate the risk of injury from, or exposure to, hazardous conditions encountered while working. PPE includes, but is not limited to: 8-inch high-laced leather boots with lug soles, fire shelter, hard hat with chin strap, goggles, ear plugs, aramid shirts and trousers, leather gloves and individual first aid kits.


An increase in the flammability of fuels due to exposure to heat and convective wind ahead of a fire.


Condition or degree of being ready to cope with a potential fire situation.


Activities directed at reducing the incidence of fires, including public education, law enforcement, personal contact and reduction of fuel hazards.


Red Card

Fire qualification card issued to fire rated persons showing their training needs and their qualifications to fill specified fire suppression and support positions in large fire suppression or incident organization. Also, sometimes referred to as IQCS card.


Smoldering Fire

A fire burning without flame and barely spreading.

Spark Arrester

A device installed in a chimney, flue or exhaust pipe to stop the emission of sparks and burning fragments.

Spot Fire

A fire ignited outside the perimeter of the main fire by flying sparks or embers.


Behavior of a fire producing sparks or embers that are carried by the wind and start new fires beyond the zone of direct ignition by the main fire.

Structural Fire Engine Company

Firefighters assigned to an engine for structural fire purposes.

Structure Fire

Fire originating in and burning any part or all of any building, shelter or other structure.


An agent, such as water or foam, used to extinguish the flaming and glowing phases of combustion when directly applied to burning fuels.


All the work of extinguishing or containing a fire, beginning with its discovery.




See also

Volunteer Fire Department (VFD)

A fire department of which some or all members are unpaid.