Fire alarm glossary for the NICET exams

391 fire alarm terms from the NICET Fire Alarm Systems content outlines and the practice questions, with short definitions. Many have a formal definition in NFPA 72 Chapter 3: knowing the exact term helps you find it in the index of your printed code.

0.7S rule: Layout check that every point on the ceiling is within 0.7 times the spacing of a detector (21 ft for 30 ft smoke spacing).
Abandoned equipment: Fire alarm equipment no longer in use. NFPA 72-2022 requires it to be removed and to be marked "not in service" until it is removed.
Abandoned fire alarm cable: Cable not terminated at equipment and not identified for future use with a tag; its accessible portion must be removed.
Above finished floor (AFF): The reference for mounting heights, measured from the finished floor.
Accessory occupancy: A minor use, generally no more than 10% of the story area, that follows the main occupancy (Section 508.2).
Acoustically distinguishable space (ADS): Zone or subdivision with its own acoustic characteristics in which voice intelligibility is planned and evaluated.
Action level: Exposure that triggers measures such as monitoring or conservation programs (for example, 85 dBA for noise).
ADDIE: Instructional design model: Analysis, Design, Development, Implementation, Evaluation.
Addressable device: Component with its own identification whose status can be individually identified or that individually controls functions.
Affected employee: A person who operates or works near the locked-out equipment; must be notified before and after the lockout.
AHJ: Authority having jurisdiction: the organization or person that enforces the code or approves the installation.
Air sampling (aspirating) detector: System that draws air through a network of pipes with sampling holes and analyzes it at a central detector.
Air-sampling detector: System that draws air through pipes with sampling ports to a central detector; ports count as spot detectors.
Air-sampling-type detector: A system that draws air through a network of sampling pipes to a central detector; each sampling port counts as a spot-type detector.
Alarm load: Current the system draws with the alarm notification appliances operating; it is carried for 5 minutes (15 for voice) in the battery calculation.
Alarm signal: Signal that results from the manual or automatic detection of an alarm condition.
Alarm verification: Feature that resets a smoke detector and confirms the alarm before reporting it; limited to 60 s.
Alarm verification feature: Feature that requires smoke detectors to confirm the condition for a period, or after a reset, to reduce unwanted alarms.
Alternating current (ac): Current that periodically reverses direction; 60 Hz in the U.S.
Ambulatory care facility: A Group B facility giving outpatient care that can leave patients unable to save themselves; it triggers a fire alarm system regardless of load.
Amended construction documents: Revised documents submitted for approval when changes during construction depart from the approved set.
Ampere-hour (Ah): Battery capacity: the current multiplied by the time the battery can deliver it.
Analog value: Numeric reading a detector sends the panel; a value far above its neighbors suggests contamination.
Approved: Acceptable to the AHJ.
Approved as Noted: A review action that lets work proceed with the reviewer's corrections; Revise and Resubmit does not.
Architect / engineer: The design professional who administers the contract, reviews submittals, answers RFIs, and certifies payment and Substantial Completion.
Assured equipment grounding conductor program (AEGCP): Written alternative to GFCIs on construction sites: daily inspection and continuity and connection tests every ≤ 3 months.
Atrium: A vertical opening through floors, closed at the top, other than stairs, elevators or shafts; the fire alarm trigger of Section 907.2.14 applies when it connects more than two stories.
Attendant: Person who stays outside the confined space, monitors the entrants, and summons rescue.
Authority Having Jurisdiction (AHJ): Organization, office, or individual responsible for enforcing the code or approving equipment, materials, installations, or procedures.
Authorized employee: The person who applies lockout/tagout to service or maintain the equipment.
Automated external defibrillator (AED): Device that analyzes the heart rhythm and delivers a shock if needed.
Average ambient sound level: The A-weighted RMS level measured over the period when people are present, or 24 hours, whichever is less.
Barrier: Fixed divider that allows PLFA and power conductors in the same enclosure (760.136(B)).
Baseline ohmic value: The reading recorded on each battery cell/unit when installed (or supplied by the manufacturer) and used for later comparison.
Beam pocket: The ceiling area between two beams; deep beams may require a smoke detector in each pocket.
Bid bond: Surety guarantee that the bidder will sign the contract and furnish required bonds if awarded.
Box fill: Calculation of the minimum box volume based on the conductors and devices it contains (314.16).
Branch circuit: Conductors between the final overcurrent device and the outlets; the FACU branch circuit must not supply other loads.
Cable substitution: Using a cable with equal or better fire performance in place of the one required, per Table 760.154(A).
Cable tie: Cable fastener; nonmetallic ties used in plenums must be listed for low smoke and heat release.
Candela (cd): Unit of effective light intensity used to rate visible notification appliances.
Capacity margin: Factor applied to the calculated ampere-hours to allow for battery aging (1.25 in the 2022 edition per industry summaries).
Ceiling-height multiplier: Factor from Table 17.6.3.5.1 that reduces heat detector spacing on ceilings between 10 and 30 ft.
Central / proprietary / remote supervising station: Types of stations that receive signals away from the protected premises (Ch. 26).
Central station: A listed supervising station providing central station service, including immediate retransmission of alarms.
Certificate of occupancy: The building official's authorization to occupy a building; a temporary certificate may cover a portion that can be occupied safely (IBC §111).
Change order: A document that authorizes a change in the contract's scope, cost, or schedule.
Circuit integrity (CI) cable: Cable rated to keep a circuit operating for a period (1 or 2 h) under fire conditions.
Circular mil (cmil): Unit of conductor area used in NEC Table 8 (14 AWG = 4110 cmil).
Claim: Demand by Owner or Contractor for an adjustment of terms, payment of money, or extension of time; notice within 21 days (A201-2017 §15.1.3.1).
Class A / X pathway: Redundant pathway that tolerates a single open; Class X also tolerates a short.
Class D pathway: A fail-safe pathway: loss of the pathway causes the intended function to occur.
Common path of egress travel: Part of the exit access travel distance before occupants have separate access to two exits or exit access doorways.
Compatibility listing: Manufacturer and listing information showing which devices may be connected to a given control unit circuit.
Compensatory measure: Alternative means, such as a person at a manual control, that performs a function while the automatic function is out of service.
Competent person: Person capable of identifying existing and predictable hazards and authorized to take prompt corrective measures (1926.32(f)).
Concretetight fitting: EMT coupling or connector made so that concrete cannot enter the raceway; required where EMT is embedded in concrete.
Conduit fill: Percentage of a raceway's interior area occupied by conductors or cables (NEC Ch. 9, Table 1).
Conflict of interest: Situation in which a personal interest could influence, or appear to influence, professional judgment; disclose it in writing when it cannot be avoided.
Construction Change Directive (CCD): Order signed by owner and architect directing a change before price or time is agreed.
Control capability: Ability of a detector with a control output to operate its relay even when other devices on the same circuit are in alarm.
Control valve supervisory switch (tamper): Sends a supervisory signal when the valve is closed; must operate within 2 revolutions or 1/5 of the travel.
Correction factor (battery): The 1.25 multiplier NFPA 72-2022 applies to the calculated amp-hours (the earlier editions used a 20 percent margin).
Cost-plus contract: Actual documented cost plus a fee for overhead and profit.
Crashing: Adding resources to critical-path activities to shorten the schedule, at added cost; take the lowest cost per day first and re-check the network.
Critical path: The longest chain of dependent activities; it sets the project duration and has zero float.
Critical path and float: The longest chain of dependent tasks sets the project length; float is how far a task can slip without delaying the finish.
Current (I): Flow of electric charge, measured in amperes (A) with the ammeter in series.
DACT: Digital alarm communicator transmitter: dials the supervising station over a telephone line and requires a second transmission means.
dBA: A-weighted sound level in decibels, the measure used for audibility requirements.
Dedicated branch circuit: Branch circuit that supplies only the fire alarm system; required for the primary power supply (§10.6.5.1).
Deferred submittal: A portion of the design, such as fire alarm shop drawings, submitted after the permit with prior approval (Section 107.3.4.1).
Deficiency: A condition that affects system performance; it must be corrected and, if not corrected at the end of the visit, reported in writing within 24 h.
Delayed-egress locking system: Lock that delays door release for a short period after the release device is pushed and an alarm sounds.
Designated level / alternate level: Floors to which elevators are sent on Phase I recall, depending on which detector operates.
Designated representative: Person or company to whom the owner assigns ITM responsibility by contract or lease.
Device schedule: Table listing each device with type, location, address, and settings such as candela.
Disconnecting means: Device that disconnects a circuit from its source; for fire alarm it has red identification and is labeled 'FIRE ALARM CIRCUIT'.
Documentation cabinet: A cabinet labeled SYSTEM RECORD DOCUMENTS where the record documentation is stored (§7.7.2).
Double-action manual box: A manual fire alarm box that needs two motions, such as lifting or pushing a cover and then pulling the handle.
Drift compensation / maintenance alert: Feature that adjusts the detector for accumulated dirt and warns when it needs cleaning.
Duct smoke detector: A detector listed to sample the air inside an HVAC duct, used to control the spread of smoke.
Duplicate address: Trouble that occurs when two devices on an SLC have the same address.
Duty rating: Maximum ladder load (person + tools + material): IAA 375, IA 300, I 250, II 225, III 200 lb.
Earned value (EV): Budgeted value of the work actually performed; CPI = EV ÷ AC and SPI = EV ÷ PV.
ECF interface device: The fire alarm system component that connects to an emergency control function, such as the relay that recalls an elevator.
Effective ground-fault current path: Low-impedance path that allows the overcurrent device to operate; the earth is not considered one.
Effective intensity (candela): The light output rating of a visible notification appliance used in the room spacing tables.
Effective intensity (cd): The luminous intensity of a flashing light expressed as an equivalent steady light; it is the cd value used in the spacing tables.
Electrical metallic tubing (EMT): Thin-wall metal raceway; FPL and FPLR are permitted inside it in plenums (Table 760.154).
Emergency control function (ECF): A building safety function started by the fire alarm system, such as elevator recall, fan shutdown, or door release.
Emergency control function interface device: Relay or module that connects the FACU to elevators, HVAC, doors, etc.; within 3 ft of the controlled component (§21.2.4).
Emergency impairment: Unplanned loss of a system, component, or function, for example from lightning, fire, or flood.
Emergency voice/alarm communication system (EVACS): A system that gives spoken evacuation instructions (Section 907.5.2.2), required for example in high-rises and large assembly.
End-of-discharge voltage: Lowest battery voltage at which the panel still operates, about 20.4 V on a 24 V system; the worst-case starting voltage.
End-of-line (EOL) resistor: A resistor at the end of a Class B circuit that lets the panel supervise the continuity of the wiring.
End-of-line device (EOL): A resistor or other device at the end of a Class B circuit that allows the wiring to be monitored for integrity.
Energy-isolating device: Breaker, disconnect, or valve that physically prevents the transmission of energy; a push button is not one.
EOL resistor: Resistor at the last device that lets the panel supervise a Class B circuit.
Equipment grounding conductor (EGC): Conductor that connects the metal parts of equipment back to the source so ground faults are cleared.
Equivalency: Use of a system, method, or device of equivalent or superior effectiveness, shown by technical documentation and approved by the AHJ (§1.5).
Executive software: The control unit manufacturer's firmware or operating system; a change requires a 10% functional test.
Exhibit: A drawing, table, or diagram that accompanies an exam question.
Exit: Portion of the means of egress between the exit access and the exit discharge, such as an enclosed interior exit stairway.
Exit access: Portion of the means of egress that leads from any occupied space to an exit (rooms, aisles, corridors).
Exit discharge: Portion of the means of egress between the end of an exit and a public way.
Exit marking audible notification appliance: A directional sounder that guides occupants to exits and areas of refuge (§18.4.8).
Exposing employer: An employer whose employees are exposed to a hazard it did not create (OSHA multi-employer policy).
F rating: Time a through-penetration firestop system resists flame passage in the standard fire test.
F rating / T rating: F: time the system blocks flame passage. T: time before the unexposed side rises 325 degrees F; T is also required in floors.
Fast tracking: Overlapping activities that were planned in sequence to shorten the schedule; it raises rework risk.
Fault isolation module: SLC device that isolates a shorted segment so the rest of the loop keeps operating.
Fault isolator: Device that separates a shorted section so the rest of the SLC keeps operating (Class X).
Field of view: The area an observer can see from one position; it determines whether strobes must be synchronized.
Fire alarm circuit: The portion of the wiring and connected equipment powered and controlled by the fire alarm system; PLFA or NPLFA.
Fire alarm control unit (FACU): Component with primary and secondary power that receives signals from initiating devices or other control units and processes them to operate the required outputs.
Fire area: The floor area enclosed by fire walls, fire barriers, horizontal assemblies or exterior walls, used for sprinkler thresholds.
Fire barrier: A fire-resistance-rated wall assembly (Section 707) that continues through concealed spaces to the deck above.
Fire command center: A rated room, required in high-rises, that houses the annunciator, voice alarm control and other fire department controls (Section 911).
Fire damper / smoke damper: Dampers in ducts at rated walls or smoke barriers (Section 717); smoke dampers close on a signal from a smoke detector.
Fire warden: Building staff member or tenant trained to perform assigned duties during a fire emergency.
Fire watch: Approved mitigating measure: personnel who patrol the building while the system is out of service.
Firestop: Listed system that seals a penetration of a fire-rated assembly so the rating is maintained.
Firestopping: Approved sealing of penetrations in fire-resistance-rated walls, floors, or ceilings (300.21).
Fixed-temperature detector: Responds when its sensing element reaches a preset temperature (for example, 135°F or 194°F).
Float: How long an activity can slip without delaying the project.
Free fall: Distance a person falls before the system starts to slow the fall; 6 ft maximum.
Free float: Time an activity can slip without delaying the early start of any successor.
General contractor: The prime contractor responsible for supervising and coordinating all trades and for jobsite safety.
Graphic (bar) scale: A bar drawn on the sheet that stays valid even when the drawing is printed reduced.
Gross margin: Profit as a percentage of the selling price: price = cost ÷ (1 − margin).
Ground fault: Unintended connection of a circuit conductor to ground (conduit, box, structure).
Ground-fault circuit interrupter (GFCI): Device that opens the circuit when it detects leakage current to ground; protects people from shock.
Guardrail system: Top rail, midrail, and posts that prevent falls from an edge.
Half-splitting: Troubleshooting technique that opens the circuit at its midpoint to eliminate the good half at each step.
Hard short: A direct, near-zero-ohm connection between two conductors.
High-rise building: A building with an occupied floor more than 75 ft above the lowest level of fire department vehicle access.
Hotspot item: A question answered by clicking on an area of the figure.
Impairment: Abnormal condition, planned or emergency, in which a system, component, or function is out of order.
Informational note: Explanatory NEC material that is not an enforceable requirement (90.5(C)).
Initial acceptance test: Inspection and test of a new system under Chapter 14, with the AHJ notified beforehand (§14.4.1).
Initiating device: Component that originates transmission of a change-of-state condition, such as a smoke detector, manual fire alarm box, or supervisory switch.
Initiating device circuit (IDC): Circuit of initiating devices whose signal does not identify the individual device that operated.
Input/output matrix: A table showing which outputs each input produces; an accepted form of the sequence of operation (Figure A.14.6.1.1).
Inspection: Visual examination of equipment to verify its location and condition and that nothing has changed or been damaged (Table 14.3.1).
Inspector's test connection: Sprinkler system outlet that simulates the flow of one sprinkler to test the waterflow switch.
Insulation resistance test: High-voltage (megohmmeter) test of insulation between conductors and to ground; devices and panel must be disconnected.
Interface device: The relay or module that connects the fire alarm system to the equipment performing an emergency control function.
Inverse-square law: In free field, sound pressure level drops about 6 dB each time the distance doubles.
Ionization smoke detection: A principle that uses a small radioactive source to ionize the air; smoke reduces the ion current and causes an alarm.
KT (temperature factor): Correction used in the battery load-test capacity calculation; 1.0 at 77°F (25°C).
L rating: Air leakage rating of a penetration firestop system in a smoke barrier.
Labeled: Bearing the label, symbol, or mark of an evaluation organization acceptable to the AHJ.
Lead time: Time from placing an order to delivery of the item; in scheduling software it can also mean an overlap between linked activities.
Legend: The table on a drawing that defines each symbol and abbreviation (symbols per NFPA 170).
Level of exit discharge: The story where an exit ends and the exit discharge begins; 'above or below' triggers are counted from it.
Lien waiver: Document releasing lien rights; a conditional waiver takes effect only when payment is received.
Line seizure: DACT ability to take over a telephone line from other equipment to send a signal.
Listed: Included in a list published by an organization acceptable to the AHJ that evaluates products and periodically inspects production.
Listed compatible: Evaluated by a testing laboratory for use with a specific control unit, not merely listed on its own.
Listed spacing: The maximum spacing between heat detectors determined by the listing laboratory and published by the manufacturer (the S value).
Lockout/tagout (LOTO): Procedure to isolate energy with locks and tags and verify zero energy before work.
Loop resistance test: Measurement of a circuit pair with the far end shorted; the reading is compared with the manufacturer's limit and with the resistance calculated from the wire size and length.
Low-frequency signal (520 Hz): An audible signal with a fundamental frequency of 520 Hz ±10 percent, required to awaken occupants in sleeping areas.
Lump sum contract: Fixed price; the contractor carries the cost-overrun risk.
Lumped load: Calculation method that assumes all NAC current is drawn at the last appliance; gives a conservative result.
Maintenance: Work done to keep equipment operable per the manufacturer's instructions (Section 14.5).
Manual fire alarm box: Manually operated device used to initiate an alarm signal (pull station).
Manual fire alarm box (pull station): An initiating device operated by a person to send a fire alarm.
Manufacturer's published instructions: The installation, operation, and maintenance instructions that come with listed equipment.
Margin vs. markup: Margin is a percentage of the selling price (price = cost / (1 - margin)); markup is a percentage of cost.
Markup: Percentage added to cost to obtain the price: price = cost × (1 + markup).
Masked threshold (narrow band): The minimum level at which a tone can be heard in the presence of noise; the alternate method requires exceeding it by 10 dB per octave band or 13 dB per one-third octave band.
Mass notification system (MNS): A system that sends emergency messages for events other than fire, based on a risk analysis and an emergency response plan.
MasterFormat: The CSI numbering of specification sections in divisions; fire alarm is 28 31 00 in the 2004 edition and 28 46 00 in later ones.
Mechanic's lien: A claim against the owner's property by an unpaid contractor, subcontractor, or supplier.
Mechanical guard: Impact protection for a detector; it must be listed for use with that detector.
Megohmmeter (insulation tester): Instrument that applies a high dc voltage to measure insulation resistance in MΩ.
Membrane penetration: An opening in only one face of a rated wall, such as an outlet box; the IBC limits box size, total area and back-to-back placement.
Minimum hearing distance: The closest distance an occupant's ear can be to an audible appliance; the 110 dBA maximum applies there (new definition in 2022).
Mitigating measures: Steps during an impairment, such as a fire watch, that the AHJ may require.
Mitigation plan: Plan naming who contacts the communications center if a real alarm occurs during remote programming of transmitters.
Mixed occupancy (NFPA 101): Occupancies so intermingled that separate safeguards are impracticable; the most restrictive requirements apply.
Modification: After signing, a written amendment, Change Order, Construction Change Directive, or architect's minor-change order.
Monitoring for integrity: Automatic detection of opens and ground faults on conductors, annunciated within 200 s (§12.6.1).
Multi-candela (selectable) appliance: A strobe with a switch or jumper to choose the intensity (for example, 15, 30, 75, 95, 110 cd); set it per the approved drawings.
Multimeter (DMM): Instrument that measures voltage, current, and resistance depending on the function and inputs selected.
NAC power extender: Remote power supply that powers additional NACs; requires its own secondary supply.
Neat and workmanlike manner: Quality of workmanship required by 110.12 and 760.24(A): cables orderly, supported, and undamaged.
NFPA 3 and NFPA 4: NFPA 3 covers the commissioning process; NFPA 4 covers integrated testing of interconnected fire protection and life safety systems.
Nipple: Short length of conduit (24 in. or less) between boxes or enclosures; may be filled to 60%.
Nominal spacing: For spot-type smoke detectors on smooth ceilings, 30 ft (9.1 m) between detectors.
Non-power-limited fire alarm (NPLFA) circuit: Circuit powered by a source that complies with 760.41 and 760.43, up to 600 V; Parts I and II.
Nonrestorable heat detector: Detector whose sensing element is destroyed when it operates; it is not heat tested in the field.
Nonseparated occupancies: Mixed uses with no rated separation; the most restrictive Chapter 9 provisions apply to the total area (Section 508.3).
Normally open (N.O.) contact: A contact that is open at rest and closes when the device operates; the usual alarm contact of conventional initiating devices.
Notification appliance: A component (horn, strobe, speaker, etc.) activated by the system that alerts occupants with audible, visual, tactile, or textual output.
Notification appliance circuit (NAC): Circuit directly connected to notification appliances such as horns, strobes, or speakers.
Notification appliance control circuit (NACC): Circuit from a control unit or module that switches or controls notification appliances; when supervised it serves no more than one notification zone.
Notification zone: A defined area in which occupant notification is accomplished simultaneously.
Nuisance alarm: Unwanted activation caused by a non-hazardous stimulus or condition (steam, dust, cooking smoke).
Observation: A suggested improvement that is neither an impairment nor a deficiency; the owner is not required to act on it (new in 2022).
Occupancy group: The IBC classification of a building by use (A, B, E, F, H, I, M, R, S, U) that drives fire alarm, sprinkler and construction requirements.
Occupant load: The number of persons a space is designed for, found by dividing floor area by the Table 1004.5 factor for the use.
Occupant load factor: Floor area per person (gross or net) that the code assigns to a use, such as 7 ft² net for concentrated assembly.
Ohm's law: The relationship E = I × R between voltage, current, and resistance.
Ohmic test: Measurement of a battery's internal conductance, resistance, or impedance, compared with a baseline value.
Open / ground fault / short circuit: The three basic wiring faults; the pathway class defines which ones the circuit tolerates.
Open circuit: A break in the current path; the ohmmeter reads OL (infinite).
Open-grid ceiling: A ceiling of louvers or egg-crate material with large openings; detectors may be omitted below it only if the opening size, thickness, and 70 percent open-area conditions are all met.
Optical fiber cable (OFNP/OFNR/OFN): Cable installed per Article 770; OFNP for plenums, OFNR for risers, OFN/OFNG for general use.
Other space used for environmental air (plenum): Space, such as above a return-air suspended ceiling, that forms part of the air-handling system (300.22(C)).
Out of service: In the NFPA 101 annex, a significant portion of the system is not functioning (for example a whole circuit), not a single device or appliance.
Overcurrent protective device (OCPD): Breaker or fuse that protects the conductors; for the FACU circuit, its location is identified at the FACU.
Owner: The party that pays for the project and contracts with the general contractor.
Owner's manual: Narrative, sequence of operation, operator instructions, maintenance and testing description, service directory, and data sheets delivered with a new system (§7.5.4).
Parallel circuit: Several branches with the same voltage; branch currents add (like the appliances on a NAC).
Pathway: Medium (wire, fiber, radio) that connects system equipment; its performance is designated by class (Ch. 12).
Pathway class: NFPA 72 designation (A, B, C, D, E, N, X) of how a pathway is monitored and what faults it tolerates.
Pathway class (A / B): Class A has a redundant path and keeps operating with an open; Class B does not, and loses everything beyond the open.
Pathway class designation: The circuit class (A, B, X, etc.) per 12.3; shown on the drawings with the EOL location.
Pathway survivability: Ability of a pathway to keep operating during a fire; Levels 0 to 4 (§12.4).
Pathway survivability level: Designation (0 to 4) describing protection of a pathway against fire damage, such as sprinklers with metal raceway or 2-hour cable.
Payment bond: Guarantees that subcontractors and suppliers will be paid.
Performance and payment bonds: Surety guarantees that the contractor will complete the contract and that subcontractors and suppliers will be paid.
Performance bond: Guarantees that the contractor will complete the contract.
Performance-based design: A design justified by goals, criteria, and analysis rather than by prescriptive spacing or layout rules; accepted by the AHJ.
Performance-based technologies: IP or cellular communication to the supervising station (§26.6.3).
Periodic frequency: How often a component is inspected (Table 14.3.1) or tested (Table 14.4.3.2): weekly, monthly, quarterly, semiannually, annually, or at a multi-year interval; count the interval from the date of the last inspection or test.
Periodic testing: Recurring testing at the Table 14.4.3.2 frequency, whose purpose is to assure operational reliability.
Permanent records: Reproducible as-built drawings, O&M manuals, written sequence of operation, and software documentation, kept for the life of the system.
Permissible exposure limit (PEL): Maximum legal exposure, usually as an 8-hour time-weighted average (TWA).
Permit-required confined space: Confined space with a hazardous atmosphere, engulfment or entrapment hazard, or other serious hazard.
Personal fall arrest system (PFAS): Anchorage, connector, and full-body harness that stop a fall in progress.
Phase I recall: Elevators return to the designated level (or alternate level), open their doors, and leave normal service.
Phase II: Firefighters' in-car elevator operation with a key switch, after Phase I recall.
Photoelectric light-scattering detection: Smoke entering the chamber scatters light onto a photosensor; responds well to smoldering fires with large particles.
Planned impairment: Impairment scheduled in advance, such as a control unit replacement; coordinated and mitigated before it starts.
Plenum: Space used for environmental air, such as above a return-air ceiling; requires plenum-rated cable or metal raceway.
Point-to-point diagram: Wiring drawing showing each conductor from terminal to terminal.
Positive alarm sequence: Automatic sequence that results in an alarm even though it may be delayed for investigation, unless reset.
Positive alarm sequence (PAS): Automatic sequence that results in an alarm even though it is delayed for investigation, unless the system is reset (15 s + 180 s).
Power (P): Energy per unit of time, in watts: P = E × I = I² × R = E² ÷ R.
Power-limited fire alarm (PLFA) circuit: Circuit powered by a source that complies with 760.121; installed per Parts I and III of Article 760.
Pre-alarm signal: Signal that results from detecting a pre-alarm condition; it must be distinctive from other signals (§10.10.8).
Pre-signal: Feature where initial signals sound only at a constantly attended location until a general alarm is started.
Pre-signal feature: Initial signal only at attended locations; the general alarm requires human action.
Pre-test: The contractor's own complete test of the system, with corrections, before the AHJ-witnessed acceptance test.
Presignal feature: A delay between the first alarm signal and general evacuation; allowed only when the AHJ and fire department approve (Section 907.5.1).
Presumed asbestos-containing material: Thermal system insulation and sprayed or troweled surfacing in buildings built no later than 1980, treated as asbestos until a survey shows otherwise (OSHA 1926.1101).
Presumed asbestos-containing material (PACM): Thermal system insulation and surfacing material in buildings constructed in 1980 or earlier.
Private mode: Signaling only to the persons directing the emergency response (for example, a nurses' station); requires 10 dB above the average ambient.
Private operating mode: Audible and visible signaling only to persons directly concerned with emergency action.
Projected beam smoke detector: Detects smoke by obscuration of a light beam between a transmitter and a receiver or reflector.
Projected beam-type detector: A line-type smoke detector that measures the reduction (obscuration) of a light beam between a transmitter and a receiver or reflector.
Projected-beam detector: Smoke detector that senses obscuration of a light beam across a space; needs stable mounting surfaces.
Proprietary supervising station: A supervising station owned and staffed by the same owner as the protected properties.
Public mode: Audible or visual signaling to the general occupants of an area; requires 15 dB above the average ambient.
Pull point: Box or conduit body where conductors can be pulled; no more than 360 degrees of bends are allowed between pull points.
Punch list: A list of items to correct or finish before final acceptance.
Qualified: A competent and capable person or company that meets the requirements and training for a given field, acceptable to the AHJ.
Qualified person: Person with the skills, knowledge, and safety training to install and operate the equipment; only such persons may access the fire alarm disconnect.
Qualified personnel: Persons who meet the evidence of qualification in Section 10.5; installers must be qualified or supervised by qualified persons.
Quality assurance / quality control: QA is the planned system that prevents defects; QC is the inspection and testing that detects them.
Quiescent load: Current the system draws in its normal condition, without alarm.
Raceway: Enclosed channel designed to hold conductors or cables, such as EMT, RMC, or rigid PVC conduit.
Radiant energy-sensing fire detector: A detector that responds to radiation (ultraviolet or infrared) from a flame or spark; requires line of sight.
Rate-compensated detector: Heat detector that operates when the surrounding air reaches its set point, regardless of how fast the temperature rises.
Rate-compensation detector: Responds when the surrounding air reaches a preset level regardless of the rate of rise, compensating for thermal lag.
Rate-of-rise detector: Responds when the temperature rises faster than a preset rate, typically about 15°F per minute.
Reacceptance test: Testing required after an addition or change to the system, scaled to what was changed (§14.4.2).
Reacceptance testing: Testing after components, wiring, or software are added, deleted, repaired, or modified (14.4.2).
Recall program: Manufacturer program to correct or replace defective equipment; the owner must be told in writing.
Record (as-built) drawings: Shop drawings updated to reflect the actual installation of the system (§7.5.5).
Record drawings: Drawings that document device and appliance locations, wiring sequences and methods, and system connections as installed (as-builts).
Record drawings (as-builts): Shop drawings updated to show the actual installation, delivered with the sequence of operation as programmed (NFPA 72 §7.5.5).
Record of completion: Document for the completed installation (Fig. 7.8.2(a)); revised after software changes.
Record of inspection and testing: Form in Fig. 7.8.2(g) and its supplements, or an equivalent alternative record, used to document periodic ITM.
Recordable case: Work-related injury or illness meeting the OSHA 1904 criteria, such as medical treatment beyond first aid, days away, or restricted work.
Redline: Field markup of the drawings that records the actual installation; the working source of the record drawings.
Redlines: A working copy of the drawings on which field changes are marked in red; used to prepare the record drawings.
Redundant path: Second path that maintains communication if the first one fails (Classes A, N, X).
Referenced standard: Document that a code adopts by reference, at the edition named in the code (for example NFPA 72 in IBC Chapter 35).
Reflected ceiling plan: A plan of the ceiling as seen from below, showing grid, lights, diffusers, and beams.
Reflected ceiling plan (RCP): A ceiling plan drawn as if reflected onto the floor; shows lights, diffusers, ceiling heights, and beams.
Regulated power supply: Supply that holds its output voltage constant over its rated load and input range.
Releasing service: FACU that actuates a suppression system (clean agent, preaction, etc.).
Remote access: Connection to a control unit from a remote device for testing, diagnostics, or software updates, with time-out and on-site personnel rules.
Request for information (RFI): A formal written question to the designer to clarify conflicts or omissions in the documents.
Resistance (R): Opposition to current flow, measured in ohms (Ω) with the circuit de-energized.
Resource leveling: Shifting work, usually within float, so that resource demand does not exceed availability; it can extend the finish date.
Retainage: Percentage withheld from progress payments until the work is complete.
Retard: A waterflow switch setting that prevents alarms from pressure surges; total activation must still occur within 90 s.
Retard (waterflow): Delay built into a waterflow switch to ride out pressure surges; the alarm must still be initiated within 90 seconds of the flow.
Retroactivity: Application of a code edition to installations that existed or were approved before its effective date; generally not required.
Reverse polarity supervision: A method in which the NAC is supervised in standby with reversed polarity (the appliance diodes block current) and the polarity is reversed in alarm to energize the appliances.
Revision cloud: A cloud-shaped outline drawn around a changed area, tied to a revision number in the revision block.
Revision cloud and delta: Cloud around a change plus a numbered triangle that ties it to the revision block.
RFI: Request for information: a written question to the designer about a conflict, omission, or unclear item.
RFI (request for information): A formal written question to the designer to resolve a conflict, omission, or unclear requirement.
Ring-back: Control unit feature that signals again when a trouble-silence switch is left in the silenced position.
Riser: Vertical cable run penetrating more than one floor or in a vertical shaft; requires riser-type cable (FPLR) or better.
Riser diagram: A building cross-section showing circuits, devices per floor, and number of conductors (§7.4.6).
Root cause: The underlying reason an event keeps recurring; corrected instead of masking symptoms.
Round-trip resistance: Resistance of the outgoing plus return conductors, used to calculate voltage drop.
Safety Data Sheet (SDS): 16-section document with a chemical's hazards, PPE, and first aid.
Secondary power supply: Batteries (or another approved source) that keep the system operating when primary power fails.
Sensitivity test: A calibrated measurement that verifies a smoke detector is within its listed and marked sensitivity range.
Sensitivity testing: Verification with a calibrated method that a smoke detector is within its listed and marked range.
Separated occupancies: Mixed uses divided by fire barriers and horizontal assemblies per Table 508.4 (Section 508.4).
Separated occupancy: Occupancies divided by fire-resistance-rated barriers so each part is evaluated under its own requirements.
Sequence of operation: A description, in matrix or narrative form, of what the system does for each signal (§7.2.1(4), §7.4.9).
Series circuit: A single current path; resistances add and the current is the same throughout the loop.
Service provider: The company or person performing service, testing, or repair; reports to the AHJ when a system is out of service more than 8 hours.
Shaft enclosure: A rated enclosure for openings through floors, such as elevator hoistways and riser shafts (Section 713).
Shall / Should: 'Shall' indicates a mandatory requirement; 'should' indicates a recommendation that is not required.
Shop drawings: The contractor's installation drawings with device locations, riser, diagrams, and calculations; the basis for the record drawings (NFPA 72 §7.4).
Short circuit: Low-resistance connection between conductors that bypasses the load or the EOL.
Short-circuit isolator: Device that opens a shorted section of an SLC so the rest of the loop keeps operating.
Shunt trip: Automatic disconnection of elevator main-line power before sprinkler discharge (§21.4).
Side rail: Either of the two long side members of a ladder.
Signal word: "Danger" (more severe hazard) or "Warning" (less severe) on a GHS label.
Signaling line circuit (SLC): Pathway between addressable devices, interfaces, control units, or transmitters that carries multiple input and/or output signals.
Silent testing: Proving every input at the control unit without sounding the appliances, then operating the appliances and interfaces once at the end (annex to 14.4.3).
Simulated operation: A test in which a device, circuit, function, or interface is made to look operated without actually operating it; the test form must say so (14.6.4).
Single-action manual box: A manual fire alarm box that sends an alarm with one motion, such as pulling the handle.
Site-specific software: Programming unique to the installation (input/output mapping, labels, control matrix).
Sleeping area: A space intended or reasonably used for sleeping (hotel room, room with a sofa bed, on-call room); requires 75 dBA, 520 Hz, and 110 or 177 cd visual appliances.
Smoke barrier: A continuous membrane that resists the passage of smoke (Section 709); penetrations are rated for air leakage (L rating).
Smooth ceiling: A ceiling without continuous projections (beams, joists) that obstruct the flow of smoke or heat beyond what NFPA 72 allows.
Solid joist: Closely spaced projection (more than 4 in. deep, 36 in. or less on center) that restricts heat flow; heat spacing is halved across it.
Solid joist construction: A ceiling with solid members projecting down at close intervals; reduces heat detector spacing to 50 percent at right angles to the joists.
Spacing (S): The listed or nominal distance between detectors on a smooth ceiling: 30 ft nominal for smoke detectors, the listed value for heat detectors.
Special inspection: Inspection and testing by a qualified independent inspector required by the building code, such as the acceptance testing of a smoke control system.
Spot-type detector: A detector whose sensing element is concentrated at one point, like most ceiling smoke and heat detectors.
Squib: Explosive-type actuator on some suppression releasing circuits; tested with an approved flashbulb or test light.
Standby (quiescent) load: Current the system draws in its normal, non-alarm condition; it is carried for 24 hours in the battery calculation.
STI / CIS: Speech Transmission Index and Common Intelligibility Scale: numeric measures of voice intelligibility.
Stranded conductor: Conductor made of several strands; for the same AWG it has slightly more resistance than solid wire.
Stratification: When smoke stops rising because it has cooled to the temperature of the surrounding air, so it does not reach the ceiling.
Stray voltage: Unwanted voltage on installation conductors; NFPA 72 limits it to 1 V ac/dc in acceptance testing.
Submittal: A package of data sheets, shop drawings, and calculations sent for review before installation.
Substantial Completion: Stage at which the owner can occupy or use the work for its intended use; the architect certifies the date.
Supervised notification appliance control circuit: An output circuit that activates notification appliance circuits on control equipment (for example a power extender); monitored for integrity, trouble on a fault, one notification zone.
Supervised sprinkler system: System whose valves, tanks, and other conditions are monitored so an impairment produces a distinctive supervisory signal.
Supervising station: Facility that receives alarm, supervisory, and trouble signals; it must be notified before and after testing.
Supervisory current: Small current that flows through the EOL in standby; if it moves outside its window, the panel indicates trouble.
Supervisory signal: Signal for an abnormal condition in the supervision of other systems, processes, or equipment (for example, a closed valve).
Survivability level: NFPA 72 designation (0 to 4) of how well a pathway is protected from fire; independent of the pathway class.
Sync module: A listed device that sends the manufacturer's synchronization protocol to the appliances on one or more NACs.
Synchronization: Visual appliances flashing at the same time; required when more than two are in the same field of view.
T rating: Time a firestop system limits temperature rise on the unexposed side of the penetrating item to 325 °F above ambient.
T-tap: A branch taken from the middle of a circuit; on Class B IDCs and NACs it leaves sections unsupervised.
Tactile notification appliance: An appliance that alerts by touch (for example, a bed shaker); its performance is evaluated per UL 1971.
Take-off: Counting and measuring quantities of material and labor from the drawings.
Tamper switch: Supervisory switch on a normally open valve that signals when the valve leaves its open position.
Technical data sheet (cut sheet): The manufacturer's document listing current draw, voltages, candela, listing, and compatibility of the equipment.
Temporal-3 (T3) pattern: The standard evacuation signal per ANSI/ASA S3.41: 0.5 s on / 0.5 s off three times, then 1.5 s off.
Temporal-4 (T4) pattern: The CO signal: four cycles of 100 ms on / 100 ms off, then 5 s off.
Test plan: Written document that clearly establishes the scope of the testing (14.2.10).
Testing: Operating a device or system to prove that it works, using the method in Table 14.4.3.2.
Textual visual notification appliance: An appliance that displays alphanumeric or pictorial messages, such as a message sign.
Through penetration: Opening that passes completely through a fire-resistance-rated wall or floor assembly.
Through-penetration firestop system: A listed, tested assembly that restores the rating of a wall or floor where cables, pipes or conduits pass through it.
Time-weighted average (TWA): Average exposure over the work shift, usually 8 hours.
Toeboard: Low barrier (≥ 3.5 in.) at the platform edge that keeps objects from falling.
Top cap: The top of a stepladder; never used as a step.
Total float: Time an activity can slip without delaying the project finish (LS − ES).
Tourniquet: Band tightened 2–3 in. above a limb wound to stop life-threatening bleeding.
Trouble signal: Signal for an abnormal condition of the system due to a fault (open, ground, loss of power).
Type 2 sound level meter: An instrument meeting ANSI/ASA S1.4 Type 2, required to measure sound pressure levels during acceptance testing (A-weighting, FAST).
UL 864 / UUKL: UL 864 covers fire alarm control units; UUKL is the added listing category for smoke control system equipment.
Unit price contract: Payment per unit installed (device, foot) times the measured quantity.
Unregulated power supply: Supply whose output voltage follows the ac line voltage and the load.
Unwanted alarm: Alarm that does not result from a potentially hazardous condition. Subtypes: malicious, nuisance, unintentional, and unknown.
Valve supervisory switch (tamper switch): A device that sends a supervisory signal when a sprinkler control valve moves from its normal position.
Valve-regulated lead-acid (VRLA) battery: Sealed battery typical of fire alarm panels; tested semiannually and replaced or load tested every 3 years.
Verification (§7.5.8): Confirmation that functions operate per the approved plans and sequence, that documentation is complete and archived on site, and that corrective actions are confirmed in writing.
Visual notification appliance (strobe): An appliance that alerts by sight; NFPA 72-2022 calls it 'visual' (formerly 'visible').
Visual warning signal ('fire hat'): Indicator in the elevator car that flashes when a hoistway or machine room detector operates.
Voltage (E): Electrical potential difference, measured in volts (V) with the voltmeter in parallel.
Voltage drop: Voltage lost in the circuit conductors: current times conductor resistance.
Voltage drop (VD): Voltage lost in conductor resistance: VD = I × R of the complete loop.
Volume allowance: Cubic inches that Table 314.16(B) assigns to each conductor, clamp, or device when calculating box fill.
VRLA battery: Valve-regulated lead-acid battery, the sealed type used as standby power; it has its own semiannual tests and a 3-year replace-or-load-test rule.
Waterflow switch: An alarm-initiating device that detects water flowing in a sprinkler system (vane or pressure type).
Wireway: Sheet-metal trough with a hinged or removable cover used to house and protect conductors; the conductors may fill no more than 20 percent of its interior area.
Working space: Clear space in front of equipment examined or serviced while energized (110.26): 3 ft deep at 0–150 V.
Written narrative: Text describing the intent and general operation of the system (§7.2.1(1)).
Zone: Defined area of the protected premises from which a signal is received, to which a signal is sent, or in which a form of control is exercised.

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