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Fire Protection Glossary - F


Family Living Unit. One or more rooms in a single-family detached dwelling, single-family attached dwelling, multifamily dwelling, or mobile home for the use of one or more persons as a housekeeping unit with space for eating, living, and sleeping and permanent provisions for cooking and sanitation. This definition covers living areas only and not common usage areas in multifamily dwellings such as corridors, lobbies, or basements.

Fault. An open, ground, or short condition on any lines(s) extending from a control unit, which could prevent normal operation.

Field of View. The solid cone extending out from the detector within which the effective sensitivity of the detector is at least 50 percent of its on-axis, listed, or approved sensitivity.

Fire. A chemical reaction that occurs when a combustible material is exposed to oxygen during which rapid oxidation results in the release of heat, light, flame, and/or smoke.

Fire Alarm Control Unit (Panel). A system component that receives inputs from automatic and manual fire alarm devices and might supply power to detection devices and a transponder(s) or an off-premises transmitter(s). The control unit might also provide transfer of power to the notification appliances and transfer of condition to relays or devices connected to the control unit. The fire alarm control unit can be a local fire alarm control unit or master control unit.

Fire Alarm/Evacuation Signal Tone Generator. A device that, upon command, produces a fire alarm/evacuation tone.

Fire Alarm Signal. A signal initiated by a fire alarm-initiating device such as a manual fire alarm box, automatic fire detector, waterflow switch, or other device whose activation is indicative of the presence of a fire or fire signature.

Fire Alarm System. A system or portion of a combination system consisting of components and circuits arranged to monitor and annunciate the status of fire alarm or supervisory signal-initiating devices and to initiate the appropriate response to those signals.

Fire Barrier. A continuous membrane, either vertical or horizontal, such as a wall or floor assembly that is designed and constructed with a specified fire resistance rating to limit the spread of fire and that also will restrict the movement of smoke. Such barriers might have protected openings.

Fire Barrier Wall. A wall, other than a fire wall, having a fire resistance rating.

Fire Command Center. The principal attended or unattended location where the status of the detection, alarm communications, and control systems is displayed and from which the system(s) can be manually controlled.

Fire Compartment. A space within a building, that is enclosed by fire barriers on all sides, including the tip and bottom. In the provisions of fire compartments utilizing the outside walls of a building, it is not intended that the outside wall be specifically fire resistance-rated unless required by other standards. Likewise it is not intended for outside windows or doors to be protected unless specifically required for exposure protection by another section of this Code or by other standards.

Fire Protection Rating. The designation indicating the duration of the fire test exposure to which a fire door assembly or fire window assembly was exposed and successfully met all the acceptance criteria as determined in accordance with NFPA 252, Standard Methods of Fire Tests of Door Assemblies, or NFPA 257, Standard on Fire Test for Window and Glass Block Assemblies, respectively.

Fire Rating. The classifications indicating in time (hours) the ability of a structure or component to withstand fire conditions.

Fire Resistance Rating. The time, in minutes or hours, that materials or assemblies have withstood a fire exposure as established in accordance with the test procedures of NFPA 251, Standard Methods of Tests of Fire Endurance of Building Construction and Materials.

Fire-Gas Detector. A device that detects the gases produced by a fire.

Fire Safety Function Control Device. The fire alarm system component that directly interfaces with the control system that controls the fire safety function.

Fire Safety Functions. Building and fire control functions that are intended to increase the level of life safety for occupants or to control the spread of the harmful effects of fire.

Fire Warden. A building staff member or a tenant trained to perform assigned duties in the event of a fire emergency.

Fixed Temperature Detector. A device that responds when its operating element becomes heated to a predetermined level. The difference between the operating temperature of a fixed temperature device and the surrounding air temperature is proportional to the rate at which the temperature is rising and is commonly referred to as "thermal lag." The air temperature is always higher than the operating temperature of the device. Typical examples of fixed temperature-sensing elements follow.

Bimetallic. A sensing element comprised of two metals having different coefficients of thermal expansion arranged so that the effect is deflection in one direction when heated and in the opposite direction when cooled.

Electrical Conductivity. A line-type or spot-type sensing element whose resistance varies as a function of temperature.

Fusible Alloy. A sensing element of a special composition (eutectic) metal that melts rapidly at the rated temperature.

Heat-Sensitive Cable. A line-type device in which a sensing element comprises, in one type, two current-carrying wires separated by heat-sensitive insulation that softens at the rated temperature, thus allowing the wires to make electrical contact. In another type, a single wire is centered in a metallic tube, and the intervening space is filled with a substance that, at a critical temperature, becomes conductive, thus establishing electrical contact between the tube and the wire.

Liquid Expansion. A sensing element comprising a liquid capable of marked expansion in volume in response to temperature increase.

Flame. A body or stream of gaseous material involved in the combustion process and emitting radiant energy at specific wavelength bands determined by the combustion chemistry of the fuel. In most cases, some portion of the emitted radiant energy is visible to the human eye.

Flame Detector. A radiant energy-sensing fire detector that detects the radiant energy emitted by a flame. Flame detectors are categorized as ultraviolet, single wavelength infrared, ultraviolet infrared, or multiple wavelength infrared.

Flame Detector Sensitivity. The distance along the optical axis of the detector at which the detector can detect a fire of specified sized and fuel within a given time frame.

Flame Spread. The propagation of flame over a surface.

FM. Factory Mutual Engineering Corporation, 1151 Boston Providence Turnpike, Norwood, MA 02062.

Four-Wire Smoke Detector. A smoke detector which is connected to the fire alarm control unit by two, two-wire circuits. One circuit is the initiating device circuit while the other circuit provides supervised power to the detector, typically 12 VDC or 24 VDC.

Frequency Division Multiplexing. A signaling method characterized by the simultaneous transmission of more than one signal in a communication channel. Signals from one or multiple terminal locations are distinguished from one another by virtue of each signal being assigned to a separate frequency or combination of frequencies.
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Some information may be found within this web site that is reprinted with permission from one or more of the following: NFPA 70 National Electrical Code®,NFPA 72® National Fire Alarm Code®, & NFPA 101® Life Safety Code®, Copyright© NFPA, Quincy, MA 02269.

This reprinted material is not the complete and official position of the NFPA on the referenced subject, which is represented only by the standard in its entirety.