HI Fire Alarm cheat sheet

NFPA 72 is the installation, testing, and maintenance standard for fire detection and alarm systems; NFPA 70 (NEC) governs the wiring methods and power circuits that feed them.

NFPA 72 defines an initiating device circuit (IDC) as the circuit between the control unit and initiating devices, and a notification appliance circuit (NAC) as the circuit between the control unit and notification appliances.

A supervising station is a facility that receives signals from protected premises; protected premises is the location where initiating devices and notification appliances are installed.

Addressable device: a device whose individual identity is reported to the control unit; conventional (zone) device: a device whose alarm state is reported only as part of a circuit or zone.

Annunciation is the signaling of a condition by audible or visual means at the protected premises; transmission is the sending of signals to a remote location such as a supervising station.

A trouble signal indicates a fault in the system that compromises reliability; an alarm signal indicates a fire condition; a supervisory signal indicates an off-normal condition of a system or process being monitored.

Presignal and positive alarm sequence delay notification to building occupants while allowing staff response; both require specific timing, staff action, and code-permitted conditions.

Authority having jurisdiction (AHJ) is the organization, office, or individual responsible for approving equipment, installations, and procedures; the AHJ approves final acceptance.

Smoke detectors: ionization responds faster to small-particle flaming fires; photoelectric responds faster to large-particle smoldering fires; both are tested with manufacturer-listed aerosol or smoke methods.

Heat detectors: fixed-temperature units alarm at a set point; rate-of-rise units alarm when temperature rises faster than a set rate; combination units respond to either condition.

Duct smoke detectors are installed in HVAC ducts to detect smoke being recirculated or transported and typically cause shutdown of the air-handling unit on alarm.

Waterflow switches detect movement of water in a sprinkler system; valve tamper switches detect partial or full closure of a control valve and are supervised as supervisory signals.

Manual pull stations must be installed so the operable part is between 42 in and 48 in (1067 mm and 1219 mm) above the finished floor unless the manufacturer's listing permits otherwise.

Notification appliances include horns, strobes, horn/strobes, speakers, and visible signals; speakers used for voice evacuation must be listed for fire alarm use and meet intelligibility requirements.

Isolator modules limit the effect of a short circuit on an addressable loop by isolating the faulted segment so other devices continue to communicate.

Relay modules control auxiliary functions such as elevator recall, door release, or HVAC shutdown, and monitor modules supervise dry contacts from other systems.

Class A initiating circuits continue to operate through a single open or ground fault; Class B circuits may lose the affected portion of the circuit on a single fault.

Conventional IDC wiring uses end-of-line (EOL) resistors to supervise the circuit; an open circuit produces a trouble, and a short across the line produces an alarm.

Addressable initiating devices communicate individually with the control unit; the loop is supervised and typically supports Class A or Class B configurations.

Smoke detector spacing on a smooth ceiling: 30 ft (9.1 m) maximum between detectors, with the first detector within 15 ft (4.6 m) of the wall.

Detector spacing must be reduced for ceiling heights above 10 ft (3 m) using the manufacturer's or code's listed spacing adjustment.

Manual pull stations must be provided at each required exit and at locations along the path of egress so no point on a floor requires travel more than 200 ft (61 m) to reach one.

Spot-type heat detectors on a smooth ceiling: 50 ft (15.2 m) maximum spacing for the 135°F to 174°F range, with the first detector within 25 ft (7.6 m) of the wall.

Duct smoke detector sampling tubes must span the full width of the duct and be installed per the manufacturer's listing; the detector must be accessible for testing and service.

Public mode audible signals must produce at least 15 dBA above the ambient sound level or 5 dBA above the maximum sound level of at least 60 seconds duration, whichever is greater, measured 5 ft (1.5 m) above the floor.

Audible signals in sleeping areas must be at least 75 dBA at the pillow or 15 dBA above ambient, whichever is greater, and must not exceed 110 dBA at the pillow.

Visible notification appliances in public mode must be spaced per the manufacturer's listed candela rating and the room's dimensions; 15 cd is the minimum for a typical public-mode room.

Strobe candela ratings increase with room size and mounting height; listed spacing tables determine the required candela for wall-mounted or ceiling-mounted devices.

Synchronization of visible signals is required within a protected area so that strobes flash in unison, preventing seizure-inducing flash patterns.

Class A notification circuits continue to operate through a single open or ground fault; Class B circuits may lose the affected portion on a single fault.

Voice evacuation systems must deliver intelligible voice messages; intelligibility is evaluated by speech transmission index or equivalent methods per the design standard.

NAC voltage drop calculations must ensure the last appliance on the circuit receives its listed minimum operating voltage; voltage drop is computed from the total appliance load and the circuit resistance.

Secondary (battery) power must be sized to operate the system for 24 hours of standby followed by 5 minutes of alarm signaling, unless the code or AHJ requires a different duration.

Battery capacity is calculated from the total standby current and alarm current using the formula: capacity (Ah) = (standby current × standby hours) + (alarm current × alarm hours), plus a derating factor.

Batteries must be charged to 80 percent of capacity within 24 hours and to full capacity within 48 hours after a discharge.

Fire alarm circuits must be separated from other circuits; power-limited and non-power-limited wiring must be installed per the NEC and the control unit's listing.

Survivability requirements apply to circuits that must continue to operate during a fire, such as circuits serving notification appliances in high-rise buildings; these circuits need a 2-hour fire-rated pathway.

The control unit must be listed for fire alarm use and must supervise its own power supplies, battery connections, and initiating and notification circuits.

Ground fault detection is required on the system; a ground fault on a supervised circuit produces a trouble signal.

Wiring methods for fire alarm circuits must follow the NEC Articles governing Class 1, Class 2, and Class 3 circuits, and the control unit's installation instructions.

Initiating devices must be tested at the frequency specified by NFPA 72; manual pull stations are typically tested annually, and smoke detectors are tested per the manufacturer's instructions and the code's schedule.

Smoke detector sensitivity testing is required at the frequency specified by the code and after any cleaning, repair, or relocation of the detector.

Notification appliances must be tested for audibility and visibility, and the test results must be documented in the record of inspection and testing.

Battery tests include a load test to verify capacity; the battery must be replaced if it fails to meet the required capacity or if it is beyond its service life.

The record of inspection and testing must include the date, the devices tested, the results, and the name of the person performing the test.

A trouble signal must be investigated and corrected; the system must not be left in a trouble condition without notifying the responsible party and the AHJ as required.

Test methods for smoke detectors include the manufacturer's listed aerosol or smoke test method; test methods for heat detectors include a listed heat source or the manufacturer's method.

Annual inspection of the control unit includes verification of the primary power supply, the secondary power supply, and the indicating appliances.

Smoke detector spacing on a smooth ceiling: 30 ft (9.1 m) maximum between detectors and 15 ft (4.6 m) from the wall, with spacing reduced for ceiling heights above 10 ft (3 m).

Heat detector spacing on a smooth ceiling: 50 ft (15.2 m) maximum for the 135°F to 174°F range, with the first detector within 25 ft (7.6 m) of the wall.

Detectors must be installed at least 4 in (100 mm) from a wall and at least 36 in (900 mm) from an air supply diffuser to avoid dilution of smoke.

Beam detectors and air-sampling detectors have manufacturer-listed spacing and installation requirements that differ from spot-type detectors.

Manual pull stations must be located at each required exit and along the path of egress so that no point requires more than 200 ft (61 m) of travel to reach one.

Notification appliance audibility must be verified by calculation or measurement; the design must account for ambient sound levels and the attenuation of walls and doors.

Strobe coverage is determined by the listed candela rating and the room dimensions; larger rooms and higher mounting heights require higher candela ratings.

Elevator recall and other auxiliary functions must be designed per the applicable code and the elevator manufacturer's requirements, with the fire alarm system providing the initiating signal.

As-built drawings and record of completion must be retained by the building owner and made available to the AHJ; they document the installed system configuration.

The record of inspection and testing must be maintained for the period required by the AHJ and must include the date, devices tested, results, and the tester's name.

Lockout/tagout procedures apply when servicing fire alarm circuits; the system must be placed in a safe condition and the responsible party notified before disabling protection.

Personnel must be trained on the system's operation, the meaning of signals, and the procedures for responding to alarm, trouble, and supervisory signals.

Documentation must include the sequence of operations, the device list, the battery calculations, and the voltage drop calculations.

Impairment procedures require notifying the AHJ and the building occupants when a fire alarm system or a portion of it is out of service.

Records of maintenance and repairs must be retained and must identify the equipment serviced, the work performed, and the date.

Safety during testing includes verifying that notification appliances are not left disabled after testing and that all devices are restored to normal operation.