Accelerant—a substance (usually a liquid) used by arsonists to enhance burning.
Aerial ladder—a fire truck having an extension ladder that is raised and lowered using the power of the truck.
Air tanker—a fixed-wing aircraft capable of extinguishing wildland fires utilizing fire suppressants or fire retardants.
Airborne pathogens—disease-causing microorganisms.
Alarm system—equipment designed to transmit a warning signal and/or detect smoke, heat, fire, or carbon monoxide in order to alert occupants and dispatch resources.
Apparatus—commonly refers to fire service vehicles (engines, ladders, rescue truck, water tenders, etc.).
Appliance—a device (ball valve, gate valve, wye, water thief, siamese) connected to a hose line or hydrant used to control, augment, divide, or discharge a water stream or fire extinguishing agent.
Arson—a crime involving starting a fire with the intent to kill, injure, defraud, or destroy property.
Attack hose—a small-diameter hose stretched off engine apparatus by firefighters to extinguish fires inside structures.
Automated external defibrillator (AED)—a device designed to analyze the cardiac rhythm of a patient and determine if defibrillation is needed and to apply a measured dose of electrical current to restore normal rhythm of the heart
Backdraft—a fire phenomenon caused by the sudden influx of air into a compartment or room that mixes with flammable gases (carbon monoxide, hydrogen, methane) already above their ignition temperature to create an explosion.
Backfire—a fire intentionally set by wildland firefighters along the inner edge of the fireline to consume fuel in the path of a fire.
Bambi bucket—a water-carrying device slung below a helicopter.
Boiling liquid expanding vapor explosion (BLEVE)—generally relating to the failure of a pressure vessel containing liquefied gas as a result of fire impinging on the container or structural damage from impact.
Boiling point—temperature of a liquid at which it will liberate the most vapors.
Booster hose—a small-diameter rubberized hose carried on a reel of an engine apparatus.
Booster tank—an internal water container found within engine apparatus.
British thermal unit (BTU)—the amount of heat energy required to raise the temperature of one pound of water (measured at 60 degrees Fahrenheit at sea level) one degree Fahrenheit. One BTU equals 1.055 kilojoules (kJ).
Brush—refers to vegetation consisting of shrubs, plants, bushes, and small trees.
Bunker gear—firefighter protective clothing consisting of coat (jacket) and pants. The term can also refer to the entire firefighter ensemble (helmet, gloves, hood, and boots).
Calorie—a heat energy unit. The amount of heat energy required to raise the temperature of one gram of water (measured at 15 degrees Celsius at sea level) one degree Celsius.
Carbon dioxide—extinguishing agent (gas) used to smother and cool a fire.
Carbon monoxide—a flammable gas that is a deadly by-product of combustion.
Cardiopulmonary resuscitation (CPR)—application of ventilations and external cardiac compressions used on patients in cardiac arrest.
Celsius degree—temperature unit pertaining to the Celsius (centigrade) temperature scale.
Chief officer—superior officer, generally taking on the role of incident commander at a firefighting incident or emergency.
Clean agent—an electrically nonconductive, volatile, or gaseous fire-extinguishing agent that does not leave a residue upon evaporation.
Combustible—material that will ignite and burn.
Community Emergency Response Team (CERT)—citizen corps program designed to train civilians to be better prepared to respond to emergency situations and assist first responders.
Company officer—company leader, generally having the rank of lieutenant or captain.
Conduction—the transfer of heat through a medium (solid, liquid, or gas).
Confined space—an area (tunnel, trench, storage tank, sewer pipe) not designed for human habitation due to physical dimensions and lack of natural ventilation.
Confinement—operations designed to control a fire to a manageable area.
Conflagration—a fire of great magnitude that covers a wide area and crosses natural boundaries.
Convection—the transfer of heat through a circulating medium (air).
Critical incident stress debriefing—discussions among first responders conducted by professionals (counseling personnel) after particularly stressful operations. It is intended to help firefighters cope with their emotions.
Decontamination—removal of harmful substances from victims. It usually consists of removing outer clothing and washing down the victim.
Defibrillation—delivery of a measured dose of electrical current in order to regain normal rhythm of the heart.
Deflagration—an explosion that propagates at a speed less than the speed of sound.
Demobilization—removal of personnel and equipment from working at a fire or emergency operation.
Detonation—an explosion that propagates at a speed greater than the speed of sound.
Dilution—extinguishing method using water on a water-soluble material to lower its concentration and raise its flash point.
Dispatcher—a person employed to coordinate the receipt, confirmation, and transmittal of fire and emergency calls and alarm signals.
Drafting—use of suction hose and engine apparatus pump to lift water from below the level of the pump.
Drip torch—handheld device with a fuel font, burner, and igniter containing gasoline and diesel fuel used by wildland firefighters to ignite a backfire.
Dry chemical—a fire-extinguishing agent that interferes with the chemical chain reaction of combustion.
Dry powder—a fire-extinguishing agent used on combustible metals.
EMS—emergency medical service.
EMT—emergency medical technician.
Emulsification—extinguishment method using water to cause agitation of insoluble liquids to produce a vapor-inhibiting froth.
Endothermic reaction—a chemical reaction that absorbs heat.
Engine (pumper) apparatus—a fire service vehicle consisting of a water pump, portable water tank, various lengths and sizes of hose and applicable appliances, nozzles, tips, and fittings.
Engine company—firefighters assigned to work on an engine (pumper) apparatus.
Exothermic reaction—a chemical reaction that gives off heat.
Explosion—rapid expansion of gases that have premixed prior to ignition.
Extension ladder—a portable ladder with one or more movable sections that can be extended to a desired height.
Extinguisher—a firefighting device consisting of a metal container containing extinguishing agent under pressure.
Fahrenheit degree—temperature unit pertaining to the Fahrenheit temperature scale.
Fire (combustion)—rapid, self-sustaining oxidation reaction with the emission of heat and light.
Firefighter—first responder who operates at fires and emergencies performing a multitude of tasks that include fire suppression, utility emergency mitigation, and medical evaluation and treatment.
Fireground—area in and around the operational jurisdiction of firefighters.
Firehouse—station where firefighters work and fire apparatus are stored.
Fire hydrant—a source of water supply to firefighters consisting of one or more valves and outlets usually connected to a municipal water supply.
Fire inspector—a person employed to enforce the Fire Code.
Fire line—the removal of brush and foliage, by hand or machine, to form a barrier against fire spread.
Fire marshal—a person designated to prevent and investigate fires.
Fire shelter—a tentlike personal life safety device designed to be deployed quickly and entered by wildland firefighters when endangered.
Fire tetrahedron—model used to represent the growth of ignition to fire. It expands on the fire triangle by adding a fourth factor (chemical chain reaction).
Fire triangle—model used to represent the three factors—oxygen, fuel, and heat—necessary for ignition.
Fittings—devices (increasers, reducers, double male/female connections, adapters) used in conjunction with hose line couplings to solve hose connection problems.
Flammable range—the percentage mixture of vapors in air that will sustain combustion.
Flashover—fire phenomenon that occurs when all the contents of a room or compartment reach their ignition temperature and simultaneously burst into flames.
Flash point—lowest temperature at which a substance/material will emit a vapor that is ignitable in air.
Foam—an extinguishing agent created by introducing air into a mixture of water and foam concentrate.
Fog stream—a hose line stream characterized by a wide-pattern of small droplets of water.
Forcible entry—gaining access to areas through locked doors and windows with the use of specialized tools and equipment.
Free-burning (fully developed) phase—the second phase of fire development.
Friction loss—reduction in the amount of water flowing through hose or piping as a result of inner lining resistance.
Fuel—material that will burn.
Fulcrum—a pivot point or support on which a lever turns.
Gas—considered the third state of matter.
GPM—gallons per minute.
Ground ladder—portable ladder designed to be utilized manually on the fireground.
Halligan—forcible entry tool with a pointed pick and adze at right angles at one end of the shaft and a fork at the other end.
Halyard—a rope attached to extension ladders for use in raising and lowering the fly ladder.
Hard suction hose—a noncollapsible hose used for drafting water.
Hazardous material (hazmat)—substance (solid, liquid, or gas) that because of its physical and chemical characteristics is dangerous to life and the environment.
Heat—a measure of the quantity of energy inside a substance.
Helitack—specialized wildland fire crews that use helicopters to fight fires and provide for movement of personnel and equipment.
Hellfighters—personnel hired by oil well control companies to extinguish oil well fires.
Hose—cotton, rubber, or synthetic conduits used by firefighters for moving water under pressure.
Hose bed—part of engine apparatus designed to hold various types of hose for ready use at firefighting operations.
Hose bridge—a ramp used to allow vehicles to pass over hose without damaging it.
Hose couplings—ends of fire hose used to connect to other lengths of hose or to hydrants, engine apparatus pumps, and appliances.
Hose roller—device designed to be attached to the roof or windowsill to facilitate hoisting and lowering of hose line.
Hose spanner—tool used to loosen and tighten hose line couplings.
Hose strap—a tool (rope with eye-loop at one end and metal hook at the other end) used to support the weight of hose couplings when hose is stretched vertically up stairwells and fire escapes.
Hotshots—specialized wildland fire crews that are mainly used to build firelines by hand.
Hydrant wrench—a tool used to operate and open and shut down a hydrant.
Hydraulics—the study of water pressure, flow, friction loss, and water supply systems.
Hydraulic spreader (Jaws of Life)—mechanical levering tool powered by a hydraulic pump engine. It is used by firefighters to extricate trapped victims inside motor vehicles.
Ignition temperature—minimum temperature a material must be heated to for it to ignite and be self-sustaining without an external input of heat.
Incendiary device—item used by arsonists to start fires.
Incendiary fire—a fire that is deliberately set.
Incipient (growth) phase—the first phase of fire development.
Inert gas—nonflammable gas that will not support combustion.
Joule—an International System of Units (SI) heat energy unit, it represents the amount of heat energy provided by one watt flowing for one second.
K-tool—steel block with a sharp K-shaped notch on one side designed to be slipped over cylinder locks for their removal.
Kelvin degree—a temperature unit pertaining to the Kelvin absolute temperature scale.
Ladder (truck) apparatus—fire service vehicle having a motor-powered ladder and tools and equipment designed for search and rescue, access to upper floors, forcible entry, ventilation, and overhaul operations.
Ladder company—firefighters assigned to work on a ladder truck apparatus.
Lever—a device or bar turning about a fulcrum.
Master (deluge) nozzles—devices used to direct large (greater than 300 GPM) water streams.
McLeod—a combination rake and hoe wildland firefighting tool with a long handle.
Nozzle—a device attached to a hose line or appliance designed to close, open, and regulate a water stream.
Overhaul—operations designed to find hidden fire and provide complete extinguishment.
Oxidation—chemical reaction between an oxidizer (oxygen-containing substance) and fuel.
Oxidizer—a substance containing oxygen that will chemically react with fuel to start and/or feed a fire.
Paramedic—advanced life support emergency care provider.
Personal alert safety system (PASS)—an alarm device that emits a signal when a firefighter is disabled, lost, or in distress.
Personal protective equipment (PPE)—equipment worn by firefighters to protect themselves from fire, heat, smoke, toxic gases, contamination, and many other dangers associated with firefighting and medical emergencies. It includes bunker gear, helmet, hood, gloves, boots, self-contained breathing apparatus, safety goggles/glasses, latex gloves, etc.
Pole (hook)—generic name for multiple kinds of long-handled tools used for pulling ceilings, opening up walls, lifting off roofing material, and breaking windows.
Positive pressure ventilation (PPV) fans—fans designed to provide forced, uncontaminated air into a room or building to displace the by-products of fire.
Prescribed burn—controlled application of fire to wildland fuels to confine the existing fire to a predetermined area.
Pyrolysis—decomposition reaction within a solid fuel brought about by the introduction of heat that is not fast enough to be self-sustaining.
Pulaski—a wildland firefighting tool consisting of a steel head with axe blade at one end and adze blade on the other end.
Radiation—the transfer of heat through space in straight lines via electromagnetic waves.
Rankine degree—temperature unit pertaining to the Rankine absolute temperature scale.
Rescue company—an elite group of firefighters specially trained to work on a rescue apparatus.
Respirator—a full-face or half-face respiratory protection device having replaceable cartridges.
Salvage—operations designed to conserve property and minimize damage following a fire.
Self-contained breathing apparatus (SCBA)—positive pressure breathing equipment worn by firefighters during structural firefighting operations. It consists of an air cylinder, high and low pressure hoses, pressure regulator, and facepiece.
Smoke ejectors—fans primarily designed to eject smoke and toxic gases from a space, room, or area.
Smoke jumpers—specialized wildland firefighter crews who parachute from planes into normally inaccessible areas during forest fires.
Smoldering (decay) phase—the third phase of fire development.
Solubility—the percentage by weight of a liquid that will dissolve in water.
Specific gravity—the ratio of the weight of a liquid to the weight of an equal volume of water.
Spontaneous combustion—endothermic chemical reaction causing self-ignition.
Sprinkler system—a fire extinguishment system utilizing water that is distributed through piping to sprinkler heads that when activated provide an umbrella discharge pattern of water droplets onto the fire.
Standard time/temperature curve—a graph that shows the relationship of time to temperature in a standard reference study; used to estimate the severity of a fire.
Standpipe system—a fire extinguishment system utilizing water that is distributed through piping to floor outlets that permit firefighters to connect and operate attack hose lines on a fire.
Suction hose—a noncollapsible hose used to draw water up vertically into an engine apparatus during drafting operations.
Supply hose—a large-diameter hose line used to provide large amounts of water to fire apparatus, appliances, and building fire extinguishing systems.
Suspicious fire—a fire that has not conclusively been determined incendiary.
Temperature—a measure of how fast molecules are vibrating inside a substance.
Thermal conductivity—a material’s ability to conduct heat.
Thermal imaging camera—a handheld heat-detecting tool utilizing infrared rays.
Tips—devices attached to hose lines and appliances designed to shape and project a water stream.
Vapor density—the relative density of a gas/vapor as compared to air.
Ventilation—operations designed to remove heat, smoke, and toxic gases from a building or structure.
Viscosity—a measure of a liquid’s flow in relation to time.
Volunteer fire department—a fire department generally organized and manned by unpaid personnel.
Water tender—wildland firefighting apparatus having large water storage capacity.
Wet chemical—an extinguishing agent for use on kitchen fires involving unsaturated fat and vegetable cooking oils.
Wildland firefighting—operations conducted to extinguish fires in forests, nature sanctuaries, and grasslands that generally do not involve structures.