A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

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.

Firehose
See also hose, below.

Firehouse
Another term for Fire station. Where fire apparatus is stored and where full-time firefighters work.

Fireline
The part of a control line that is scraped or dug to mineral soil. Also called fire trail. More generally, working a fire is called being on the fireline." May also refer to a "wet line" where water has been used to create a burn boundary in light fuels such as grass.

Fireline handbook
A small red booklet carried by U.S. firefighters on the firelines, as a quick reference on various firefighting topics.

Fireman's key
Set of tools used for opening elevator doors from the lobby during rescues; come in many different shapes and sizes, each designed for a specific elevator type.

Firestorm
A conflagration of great enough proportions to noticeably create its own wind conditions.

Firestorm
Extreme fire behavior indicated by widespread in-drafts and a tall column of smoke and flame, where added air increases fire intensity, creating runaway fire growth.

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.

Flanks of a fire
The parts of a fire's spread perimeter that are roughly parallel to the main direction of spread.

Flare-up
Any sudden acceleration in rate of spread or intensification of the fire. Unlike blowup, a flare-up is of relatively short duration and does not radically change existing control plans.

Flash fuels
Fuels such as grass, leaves, draped pine needles, fern, tree moss and some kinds of slash, which ignite readily and are consumed rapidly when dry.

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.

Fly
The moving portions of an extension ladder.

Foam
The aerated solution created by forcing air into, or entraining air in water containing a foam concentrate by means of suitably designed equipment or by cascading it through the air at a high velocity. Foam reduces combustion by cooling, moistening and excluding oxygen.

Fog nozzle
A nozzle that discharges water in small droplets. Oftentimes, the nozzles are adjustable, permitting the pattern to range from a straight stream to a narrow fog to a wide fog stream. Can also be designed to automatically adjust pressure depending upon selected pattern.

Fog Stream
A fire stream characterized by small droplets of water. The droplets are unable to travel very far, but absorb heat very quickly because of the high surface area they present.

Foot valve
Backflow preventer at inlet of suction hose used in drafting; helps avoid losing prime by keeping water from running back out of the suction hose.

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.

Fuel load
The mass of combustible materials available for a fire usually expressed as weight of fuel per unit area (e.g., 20 tons per acre).

Fuel moisture
Percent water content of vegetation, an important factor in rate of spread, ranging from dead-fuel and fine-fuel moisture (FFM), of 10 percent or less, to live-fuel moisture (LFM), of 60 percent or more. FFM can be estimated by weighing calibrated wood sticks.

Fuel type
An identifiable association of fuel elements of distinctive species, form, size, arrangement, or other characteristics that will cause a predictable rate of spread or resistance to control under specified weather conditions.

Fuelbreak
A natural or manmade change in fuel characteristics which affects fire behavior so that fires burning into them can be more readily controlled.

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.