OK Fire Alarm Installer key terms

The National Fire Alarm and Signaling Code, published by the National Fire Protection Association. It sets minimum requirements for designing, installing, testing, inspecting, and maintaining fire detection and alarm systems in the United States.

The organization, office, or individual responsible for approving equipment, installations, and procedures. In fire alarm work the AHJ is usually the local fire marshal or building official who reviews plans and signs off on acceptance tests.

The article of NFPA 70, the National Electrical Code, that governs fire alarm systems. It covers power-limited and non-power-limited fire alarm circuits, permitted conductor types, installation methods, and wiring requirements.

Equipment or material tested by an approved testing laboratory, such as UL, and found to meet a published safety standard. Only listed components may be used in fire alarm systems unless the AHJ grants a specific exception.

A defined area or group of devices reported together by the control unit. Zones help responders locate the alarm quickly and are used to organize device addressing and annunciation on both conventional and addressable systems.

A fire alarm system in which each initiating or notification device has a unique digital address. The control unit polls devices individually and can report the exact device that alarmed or failed, which speeds troubleshooting.

A system in which devices share a zone circuit and the control unit reports only the zone, not the individual device. It is simpler and less expensive but gives responders less specific location information.

A signal indicating that a system or suppression component is off-normal, such as a closed sprinkler control valve or a low water level. It is distinct from an alarm and from a trouble and must annunciate at the control unit.

A signal indicating a fault in the system itself, such as an open circuit, grounded conductor, loss of primary power, or device failure. NFPA 72 requires it to sound and display within a set time.

A feature that briefly delays the alarm signal from a smoke detector to allow a second check, reducing nuisance alarms from transient conditions like dust or steam. It must never delay signals from manual pull stations.

The maximum distance allowed between detectors and from detectors to walls, set by code and by the device listing. For standard spot smoke detectors it is commonly 30 feet on smooth ceilings, with the first detector within 15 feet of a wall.

A detector that uses a light source and a sensor inside a chamber, where smoke scatters light into the sensor and triggers the alarm. It responds best to visible smoke from smoldering fires.

A detector that uses a small radioactive source to ionize air in a chamber and senses the change in current when smoke particles enter. It responds quickly to flaming fires that produce small particles.

A device that alarms when the temperature rises faster than a set rate, typically around 15 degrees Fahrenheit per minute. It responds to fast-growing fires but can be unreliable where temperatures swing rapidly under normal conditions.

A device that alarms when the surrounding air reaches a predetermined set point, such as 135 or 194 degrees Fahrenheit. The set point is chosen above normal ambient temperatures yet low enough to catch a growing fire.

A device on a sprinkler system pipe that senses water movement and sends an alarm signal to the control unit. A retard mechanism prevents false alarms caused by minor pressure surges when the system refills.

A hand-operated device mounted along an exit path that lets a person trigger the alarm. It must be reachable, unobstructed, and mounted at a consistent height, and its signal may not be delayed by alarm verification.

A detector installed on an HVAC duct with sampling tubes that sense smoke moving through the air stream. It typically shuts down the air handler and is required where ducts penetrate certain rated assemblies.

The standard evacuation sound made of three short pulses followed by a pause, then repeated. It is used on fire alarm horns and speakers so occupants can tell a fire alarm apart from other building signals.

The unit of luminous intensity used to rate visible notification appliances. Strobes must be selected for the room size and mounting height so they produce the light output the code requires for that space.

A system that delivers spoken messages through speakers instead of, or along with, horns. It allows tailored instructions and is often required in high-rise, assembly, and other large occupancy buildings.

The main panel that receives signals from initiating devices, processes them, and controls notification appliances. It also monitors its own circuits for trouble and provides the interface for remote annunciation and off-site monitoring.

The wiring loop or path connecting automatic detectors, manual pull stations, and other initiating devices to the control unit. The control unit supervises it continuously and reports alarm, trouble, or supervisory conditions on it.

The circuit that supplies power to horns, strobes, speakers, and other notification appliances. It is supervised so the control unit detects opens, shorts, or missing appliances on the wiring.

A circuit whose wiring leaves the control unit and returns to it on a separate path, so it keeps working with a single open or ground fault. The fault is reported as a trouble while the circuit continues to function.

A circuit wired as a single path out from the control unit. It works normally, but any open or short beyond the panel disables every device past that point and is reported as a trouble condition.

The normal commercial AC supply feeding the fire alarm control unit, usually a dedicated branch circuit. It must be connected ahead of other loads so it cannot be switched off by accident.

The backup supply, typically rechargeable batteries or an engine generator, that keeps the system running when normal power fails. NFPA 72 sets the minimum operating time based on the system type and occupancy.

A worksheet that adds up the current drawn by the control unit and all devices in standby and in alarm, multiplies by the required time, and adds a margin to select the correct battery size.

A measure of battery capacity, describing the current a battery can deliver for a stated number of hours. It is used with the load calculation and a derating factor to confirm the battery meets standby requirements.

The formal test performed after installation and before the system is placed in service. It verifies that every device, circuit, and function operates as designed and is witnessed by the owner and usually the AHJ.

A visual and physical check that the system and its components are in place, undamaged, and unobstructed. It is performed at code-specified intervals and by itself does not confirm that devices will operate.

Operating a device or circuit to confirm it produces the correct response at the control unit. Testing differs from inspection, which is a visual check, and from maintenance, which is corrective or cleaning work.

A check that a smoke detector's response falls within its listed range, done with a calibrated instrument or the manufacturer's method. Detectors that test outside the range must be cleaned, adjusted, or replaced.

Scheduled cleaning, adjustment, and replacement of system components to keep them reliable. NFPA 72 requires it after certain tests and whenever inspection or testing shows a device is dirty or degraded.

A document required by NFPA 72 that the installing contractor completes and signs at the end of a project. It records components, wiring, and test results and confirms the installation matches the approved plans.

An official authorization from the local jurisdiction to install or modify a fire alarm system. Working without one can bring stop-work orders, fines, and refusal by the AHJ to accept the finished system.

The process in which the AHJ examines submitted drawings and specifications before construction begins to confirm code compliance. Work generally may not start until the plans are approved and a permit is issued.

A procedure for isolating electrical or other energy sources and applying locks and tags so equipment cannot be re-energized while someone works on it. It protects installers and testers from shock and unexpected startup.