* Dalmatian: "Firehouse dog."
* Dead lay: A load of hose on a pumper, but not connected to a pump outlet. Often used for larger supply lines.
* Deflagration: An explosion with a propagation front traveling at subsonic speeds, as compared to supersonic detonation.
* Direct attack: "Putting the wet stuff on the red stuff." A form of fire attack in which hoses are advanced to the fire inside a structure and hose streams directed at the burning materials.
* Discharge flow: The amount of water flowing from a fire hydrant when it is opened; compare to static flow and residual flow.
* Dispatch: Refers to person or place designated for handling a call for help by alerting the specific resources necessary.
* Draft: The process of pumping water from a static source below the pump.
* Drills: training during which an emergency is simulated and the trainees go through the steps of responding as if it were a real emergency.
* Electrical fire: A fire in which the primary source of heat is electricity, resulting in combustion of adjacent insulation and other materials; may be hazardous to attempt to extinguish using water.
* EMS: Emergency medical service(s).
* Engine: A fire suppression vehicle that has a water pump and, typically, is designed to carry firehose and a limited supply of water.
* Engineer: A firefighter responsible for driving the engine to the scene of the call and operation of the pumps on an engine, to provide sufficient water to the firefighters on the hose.
* Engine Company: A group of firefighters assigned to an apparatus with a water pump and equipped with firehose and other tools related to fire extinguishment.
* Engine house: [archaic] A firehouse housing an engine company.
* Engine pressure: The pressure in a fire hose measured at the outlet of the pump.
* Enhanced 9-1-1: Electronic system for automatic correllation of physical telephone lines with information about the location of the caller -- a useful tool for dispatchers when the caller has an emergency but cannot speak.
* Evacuation: Removal of personnel from a dangerous area, in particular, a HAZMAT incident, burning building, or other emergency. Also refers to act of removing firefighters from a structure in danger of collapsing.
* Evolution: Uniform sequence of practiced steps by squad carrying out common tasks such as selection and placement of ladders, stowing hoses in hose bed, putting hoses and tools into service in particular patterns; intended to result in predictability during emergencies.
* Exothermic reaction: Chemical reaction giving off heat in the process, such as combustion.
* Explorer: a young adult who's age is between 14 and 21 who learns the basics of firefighting.
* Exposure: Property near fire that may become involved by transfer of heat or burning material from main fire, typically by convection or radiation. May range from 40 feet to several miles, depending on size and type of fire or explosion.
* Extrication: removal of a trapped victim such as a vehicle extrication, confined space rescue, or trench rescue; sometimes using hydraulic spreader, Jaws of Life, or other technical equipment.
* FAST (or F.A.S.T.): Firefighter Assist and Search Team (also called Rapid Entry Team or Rapid Intervention Team/Crew) — firefighters assigned to stand by for rescue of other firefighters inside a structure; an implementation to support the Two-in, two-out rule; may have specialized training, experience and tools. While all of these versions of the name for a firefighter rescue crew either have been used or continue to be used in several areas, the National Incident Management System (NIMS) has determined that Rapid Intervention Crew, ("RIC") will be the national term. Current U.S. federally mandated training programs are in the process of standardizing this and other terms under DHS and FEMA.
* FDC (Fire Department Connection): Location in which pumping apparatus hooks to a buildings standpipe and or sprinkler system. Usually a 3" female connection.
* Fire Break: Especially in hilly or mountainous areas, roads or paths cut through brush with a tractor, bulldozer or other construction equipment. The purpose of these is to have an area with no brush, and thus, no fuel, so that a fire will hopefully burn out rather than jumping to another area with brush. Also to ensure vehicular access to brush areas.
* Fire code ( Fire safety code): regulations for fire prevention and safety involving flammables, explosives and other dangerous operations and occupancies.
* Fire engineering: Scientific design of materials, structures and processes for fire safety
* Fire escape: A building structure arranged outside to assist in safe evacuation of occupants during an emergency; may connect horizontally beyond a fire wall or verically to a roof or (preferably) to the ground, perhaps with a counter-weighted span to deny access to intruders.
* Firefighter: People who respond to fire alarms and other emergencies for fire suppression, rescue, and related duties.
* Firefighter Assist and Search Team: See FAST.
* Fire flow: The amount of water being pumped onto a fire, or required to extinguish a hypothetical fire. A critical calculation in light of the axiom that an ordinary fire will not be extinguished unless there is sufficient water to remove the heat of the fire.
* Fireground: The operational area at the scene of a fire; area in which incident commander is in control. Also used as name of radio frequency to be used by units operating in the fireground, as in “Responding units switch to fireground.”
* Fire hazard: Materials, structures or processes that may result in creating a fire, permitting a fire to grow undetected, or preventing people from escaping a fire.
* Firehouse: Another term for Fire station. Where fire apparatus is stored and where full-time firefighters work.
* Fire hydraulics: The study of pumps, hoses, pipes, accessories and tools for moving water or other extinguishing agents from a water supply to a fire.
* Fire inspector: A person responsible for issuing permits and enforcing the fire code, including any necessary premises inspection, as before allowing (or during) a large indoor gathering.
* Fire line: A boundary of a fire scene established for public safety and to identify the area in which firefighters may be working.
* Fire load (Btu/sq ft): An estimate of the amount of heat that will be given off during ordinary combustion of all the fuel in a given space; e.g., a bedroom or a lumberyard.
* Fire marshal: Administrative and investigative office for fire prevention and arson investigation.
* Fire point: temperature at which materials give off flammable gases that will sustain fire, typically higher than flash point. Temperature at flashover.
* Fire Police: Special constables attached to a fire department, tasked with ensuring the safety and security of emergency scenes as well as general assistance to the fire department and other agencies.
* Fire prevention: Fire safety; standards for minimizing fire hazards.
* Fire-resistant: Materials designed or treated to have an increased fire point.
* Firestorm: A conflagration of great enough proportions to noticeably create its own wind conditions.
* Fire tetrahedron: The fire tetrahedron is based on the components of igniting or extinguishing a fire. Each component represents a property necessary to sustain fire: fuel, oxygen, heat, and chemical chain reaction. Extinguishment is based upon removing or hindering any one of these properties.
* Fire triangle: Model for understanding the major components necessary for fire: heat, fuel and oxygen. See also fire tetrahedron for a more comprehensive model.
* Fire wall: Building structure designed to delay horizontal spread of a fire from one area of a building to another; often regulated by fire code and required to have self-closing doors, and fireproof construction.
* Fire warden:
* Fire watch: Fixed or mobile patrols that watch for signs of fire or fire hazards so that any necessary alarm can be quickly raised or preventive steps taken.
* Fit test: Periodic test of how well the facepiece of an SCBA fits a particular firefighter.
* Flammable range, limits: The percentage mixture of fumes with air that will sustain fire; outside the limits the mixture is either too lean or too rich to burn.
* Flash point: Lowest temperature at which a material will emit vapor combustible in air mixture. Lower than fire point of same material.
* Flashover: simultaneous ignition of combustible materials in a closed space, as when materials simultaneously reach their fire point; may also result in rollover.
* Forcible entry: gaining entry to an area using force to disable or bypass security devices, typically using force tools, sometimes using tools specialized for entry (e.g., Halligan, K-tool).
* Forward lay: Procedure of stringing water supply hose from a water source toward a fire scene; compare with reverse lay.
* Freelancing: dangerous situation at an incident where an individual carries out tasks alone or without being assigned; violation of personnel accountability procedures.
* Friction loss: Reduction of flow in a firehose caused by friction between the water and the lining of the hose. Depends primarily upon diameter, type and length of hose, and amount of water (GPM) flowing through.
* Frontage: The size of a building facing a street.
* Fully involved: Term of size-up meaning fire, heat and smoke in a structure are so widespread that internal access must wait until fire streams can be applied.