NFPA 72 Fire Alarm & Signaling Code – Deep Reference & Exam Study Guide

• 1. Scope & Fundamentals
• 2. Essential Terms & System Types
• 3. Documentation & Submittals
• 4. Power Supply & Battery Calculations
• 5. Circuits, Classes, Pathways
• 6. Initiating Devices
• 7. Notification Appliances
• 8. Supervision, Integrity, and Troubleshooting
• 9. Inspection, Testing & Maintenance
• 10. Emergency & Mass Notification
• 11. Interfaces & Special Features
• 12. Practical Examples & Field Scenarios
• 13. Quick Reference Tables, Tips & Formulas

1. Scope & Fundamentals

• NFPA 72 governs:
  • Design, installation, performance, testing, and maintenance of fire alarm, mass notification, and signaling systems
  • Both prescriptive and performance-based systems in all building types
• Purpose: Life safety – early fire/smoke detection, alerting, emergency communication, fire department notification.
• Referenced codes: Closely integrated with NFPA 70 (NEC), NFPA 101 (Life Safety), NFPA 13/25 (Sprinklers), IBC/IFC.
• Exemptions: Some one- and two-family dwellings (see Chapter 29, but most apartments are covered).
• Required system types:
  • Protected Premises System: Detects, notifies, may not notify fire department
  • Supervising Station System: Transmits signals to a remote monitoring center (Central/Proprietary/Remote Supervising)
  • Emergency Voice/Alarm Communication System (EVACS): Used in high-rises, assembly, schools, etc.

2. Essential Terms & System Types

Initiating Device

Component that detects fire, smoke, heat, or manual action. Includes smoke, heat, duct, waterflow, manual pulls, and more.

Notification Appliance

Device that notifies occupants: horns, strobes, speakers, bells, chimes.

Addressable System

Each device has a unique identifier for location/troubleshooting; shows specific device status on the panel.

Conventional (Zoned) System

Devices wired in parallel; panel shows zone/area, not specific device.

Class A/B Circuits

Class A: loops with return path, survive single break; Class B: simple loop, downstream fail on open.

Pathway Survivability Levels

Level 0: none. Level 1: 2-hour protection. Level 2: redundant or 2-hr + separated. Level 3: 2-hr, fully separated, redundant risers (e.g. high-rise voice evac).

Supervisory Signal

Signals non-fire issue (sprinkler valve closed, air pressure low, etc.).

Trouble Signal

Indicates wiring, device, battery, or ground fault.

Alarm Verification

Panel delays alarm for short period (e.g., 30s) to verify transient signals before full alarm.

Silence Function

Allows horns/bells to be silenced; strobes continue to flash until reset.

Type	Description	Exam Tip
Initiating Device	Smoke/heat/manual/waterflow, detects hazard	Requires zone/address, must be supervised
Notification Appliance	Warns (horn/strobe/speaker/bell)	Strobes must be synchronized in same area
Supervisory	Valve closed, air pressure, temperature	Yellow light, distinct from alarm
Trouble	Open, short, ground, battery, device fault	Must annunciate within 200 seconds

3. Documentation & Submittals

• Shop Drawings must include:
  • Legend and symbol key
  • Riser diagram (showing devices, zones, notification circuits, and supervision)
  • Floor plans with all devices, circuit numbers, candela settings, speaker wattage
  • Conduit/wire types, sizes, and classes; color coding for notification vs initiating
  • Details of ceiling heights, wall construction, and device mounting heights
• Battery Calculations:
  • Must provide 24 hours standby + 5 minutes in alarm (voice evac = 15 min alarm)
  • Calculate total standby load + total alarm load, then size battery for worst-case scenario (usually both not at once)
  • Include NAC circuit inrush current for worst-case scenario
• Voltage Drop Calculations (NAC):
  • Required for all notification circuits; must verify voltage at end-of-line ≥ minimum device rating
  • Example: 18AWG, 100 ft run, 1A load: Vdrop = 2 × L × I × R/1000
• Record of Completion:
  • Filled out after acceptance testing; includes as-built drawing, device serials/addresses, testing results, installer and AHJ signatures
• Maintenance & Test Records:
  • Must be kept at the protected premises until the next test plus 1 year (minimum)

Field Note: AHJs will frequently reject plans that do not show room names/numbers, device addresses, or sequence of operations clearly. "Missing details = failed permit!"

4. Power Supply & Battery Calculations

• Primary Power:
  • Dedicated 120 VAC or 240 VAC branch circuit, marked red, labeled "FIRE ALARM CIRCUIT" at panel and breaker
  • No other loads allowed on this circuit (e.g., no outlets, lighting, or non-fire equipment)
  • Breaker lock required (to prevent accidental shutoff)
• Secondary Power:
  • Batteries (sealed lead-acid or NiCd)
  • Must supply system in standby for 24 hours (or 60 hrs for auxiliary alarm systems, e.g., rural applications), plus 5/15 minutes full alarm
• Battery Sizing Example:
  • Standby: 100 mA × 24 hrs = 2.4 Ah
  • Alarm: 800 mA × 5 min = 0.07 Ah
  • Total: 2.4 + 0.07 = 2.47 Ah (multiply by 1.25 for safety margin = 3.09 Ah)
  • Round up to next battery size (e.g., 4.5 Ah battery pair)
• Generator (optional/required in high-rise or critical facilities):
  • Must transfer power to alarm system within 10 seconds of utility failure
• Ground Fault Detection: All power and circuit wiring must be monitored; ground fault must trigger trouble within 200 seconds.

5. Circuits, Classes, Pathways

Class	Description	Fault Tolerance	Typical Use
A	Loop with return path to panel (four wires)	Single open does not disable devices; both sides needed for full operation	Critical detection (addressable SLC)
B	One-way loop (two wires)	Single open disables devices past the break	Conventional detection
C	Multiple pathways, point-to-point	Single open may/may not disable devices	Special signaling, usually not used for detection
D	Fault-tolerant via redundancy, diversity	Survives any single open or short	High reliability (e.g., military)

• Pathway Survivability: Applies to critical circuits (voice evac, elevator recall, smoke control):
  • Level 0: None
  • Level 1: 2-hour fire-rated cable/conduit
  • Level 2: As Level 1 + separation from hazards
  • Level 3: Two fully redundant, 2-hour-rated risers
• End-of-Line (EOL) Resistor: Required at the last device of each Class B circuit for supervision
• Voltage Drop (Notification): Must not fall below device minimum; maximum NAC length determined by calculations

6. Initiating Devices

Manual Devices

• Manual Pull Stations:
  • Required within 5 ft of exit doors, on every floor
  • Travel distance to nearest pull: max 200 ft
  • Installed 42–48" AFF (above finished floor)
  • Double-action recommended (e.g., lift and pull)

Automatic Devices

• Smoke Detectors:
  • Corridor, sleeping areas, elevator lobbies, electrical rooms
  • Spacing: 30 ft apart max on smooth ceiling; adjust for ceiling height and obstructions
  • Placement: Not within 36" of supply diffusers or cooking appliances; not above ceiling tiles unless plenum-rated
• Heat Detectors:
  • Used in dusty, humid, or kitchen areas
  • Types: Fixed temperature, rate-of-rise, combination
  • Spacing: up to 50 ft (check device listing and Table 17.6.3.5.1)
• Duct Detectors:
  • Required on air-handling units ≥2,000 cfm
  • Sample tubes must span the entire duct width
  • Test switches must be accessible
• Waterflow & Supervisory Switches:
  • Alarm within 90 seconds of flow (wet), 5 minutes (dry)
  • Tamper switches on all control valves

Exam Tip: Know where smoke detectors are NOT required: mechanical rooms (unless required by AHJ), bathrooms with shower/tub, non-habitable attics/closets.

7. Notification Appliances

Audible Notification

• Evacuation signal: Temporal-3 pattern ("beep beep beep...pause...")
• Alarm must be at least 15 dBA above average ambient, or 5 dBA above maximum ambient (for >30 seconds)
• Sleeping rooms: 75 dBA at pillow level minimum
• Low frequency (520 Hz) sounders required for new sleeping rooms (hotels, dorms, apartments)
• Speaker systems: must provide intelligible messages (STI ≥0.7 recommended); coverage verified by testing

Visible Notification (Strobes)

• Minimum 15 candela (cd) in public spaces; higher in large/open areas
• Mounting height: 80–96" above finished floor
• Spacing: Based on device candela rating; see Table 18.5.5.4.1(a)
• Synchronization required if more than one strobe in the same room/area
• Wall- and ceiling-mounted strobes must be labeled for their mounting orientation

Space Type	Min. Sound Level	Strobe Candela
Sleeping Room	75 dBA at pillow	110 cd at bed
General Area	15 dBA over ambient	15 cd (public); 75–110 cd (large)
Restroom	15 dBA over ambient	75 cd

Field Tip: Don't mount strobes next to strong lighting or in direct sunlight—flash may not be visible in those conditions.

8. Supervision, Integrity, and Troubleshooting

• All circuits supervised for open, short, ground faults; loss of supervision triggers panel trouble within 200 seconds
• Addressable systems: Panel polls every device; if device goes missing, panel displays address and triggers trouble
• Class A circuits survive a single break; both directions must be intact for normal operation
• Ground fault: Any contact between signal wire and earth/metal; must annunciate and not disable other system functions
• Common troubles: missing EOL resistor, loose wire, dirty smoke detector, device removed, voltage drop too high on NAC
• Trouble logs must be reviewed after every service, and issues documented and cleared

Trouble Signal	Likely Causes	Solution
Open Circuit	Wire cut, EOL missing, device removed	Check continuity, replace EOL, inspect wiring/devices
Short Circuit	Wires crossed, device/panel failure	Isolate by zone/section, replace shorted cable/device
Ground Fault	Wire touching ground/metal, water intrusion	Megger or ground-fault meter, isolate branch
Device Fault	Dirty detector, missing base, wrong address	Clean, readdress, replace device
Low Battery	Failed battery, charging issue	Replace battery, test charger

9. Inspection, Testing & Maintenance

• Initial Acceptance Testing: 100% of all devices and circuits must be tested in presence of AHJ and owner
• Regular Maintenance:
  • Monthly: Visual check of control panel, indicators, batteries
  • Quarterly: Waterflow/tamper switches (if sprinklered), select smoke/heat detectors
  • Semiannual: All notification appliances, duct detectors, remote annunciators, manual pulls
  • Annual: 100% of all devices and system functions, plus backup power load test
  • Batteries: Monthly visual, annual load; replace as needed (typically every 3–5 years)
• Test Records: Must be kept on site until the next test plus 1 year (often longer for healthcare/critical facilities)
• Impairments: Any planned shutdown or disabling of a system must be documented, with owner/AHJ notification and fire watch as required
• System Upgrades: Must be retested, with new ROC (Record of Completion) filed

Device/Component	Inspection/Test Frequency
Smoke Detectors	Annual functional test; semiannual sensitivity test
Manual Pull Stations	Annual
Sprinkler Waterflow Switches	Quarterly (wet), semiannual (dry)
Notification Appliances	Semiannual (visible), annual (audible)
Control Panel	Monthly (visual), annual (function)
Batteries	Monthly (visual), annual (load test)

10. Emergency & Mass Notification

• Emergency Voice/Alarm Communication (EVACS):
  • Required in high-rise, large assembly, and certain education and healthcare occupancies
  • Must deliver clear, intelligible messages to all areas (STI ≥0.7)
  • Pre-recorded and live microphone for fire dept use
• Mass Notification Systems (MNS):
  • Used for weather, terrorist, or civil emergency; must be distinct from fire alarm
  • Priority: Fire alarm always takes precedence; MNS may use same speakers with distinct signals
• Two-Way Communication: Required in areas of refuge, elevator lobbies, and certain stairwells; must ring to 24/7 attended location
• Firefighter Phones: Handsets required in high-rise stairwells, elevator lobbies, and fire command centers
• Annunciation: Remote annunciator required at main entrance or fire command center, showing all zones and device status

Field Example: In a 12-story apartment, an EVACS must deliver clear evacuation instructions on all floors, with automatic message repeats every 2 minutes until reset.

11. Interfaces & Special Features

• Elevator Recall: Fire alarm triggers return of all cars to recall floor, disables normal operation until reset by fire department
• HVAC Shutdown: Duct detectors, smoke dampers shut down air handling to prevent smoke spread
• Door Release: Fire doors on magnetic holders close on alarm; unlocks stairwell doors for fire department access
• Sprinkler Monitoring: Waterflow, pressure, and tamper switches all monitored and annunciated
• Access Control Interface: Fire alarm unlocks secure doors for evacuation
• Building Automation Integration: Fire alarm signals may override lighting, HVAC, access controls per approved sequence

Installer Note: All interfaces must be tested and witnessed by AHJ and owner; simulated fire alarm must cause all required functions to operate as intended.

12. Practical Examples & Field Scenarios

Example 1: School Fire Alarm Upgrade

• New system replaces conventional panel with addressable SLC
• Manual pulls at each exit, horns and strobes in all classrooms, synchronized corridor strobes, door holders released on alarm
• Annual testing: Each device tested and result logged; teacher disables a smoke detector with a plastic cover—trouble signal at panel

Example 2: High-Rise Voice Evac

• 12-story office, 2-hour rated risers, dual redundant voice panels
• Message: "Attention, attention, there has been a fire emergency reported in the building. Please proceed to the nearest exit."
• Panel fails over to backup on main riser short; fire department can use microphone to broadcast instructions

Example 3: Warehouse NAC Voltage Drop

• Longest notification appliance circuit is 350 ft, 18AWG, 1.2A total load
• Calculation shows voltage at last strobe is 18.1V (above 16V required by device)—approved
• If below, must use thicker wire or split into multiple NACs

Example 4: Assisted Living Facility Testing

• Every smoke, heat, and pull station tested annually
• All notification devices measured for required dBA/candela in all rooms
• Results logged and signed by technician and building representative

Example 5: Restaurant Remodel

• Remodel triggers fire alarm upgrade; must submit new shop drawings and battery/NAC calcs
• Existing wiring re-used where allowed (must be tested and in good condition)
• Sequence of operations reviewed by AHJ; acceptance test includes fire department notification

13. Quick Reference Tables, Tips & Formulas

Requirement	NFPA 72 Standard Value	Field Note
Max. pull station spacing	200 ft travel distance	Each exit, each floor, 42–48" AFF
Smoke detector spacing	Max 30 ft apart	Adjust for ceiling height, airflow
Sound level, general area	≥15 dBA above ambient	75 dBA at pillow in sleeping rooms
Strobe mounting height	80–96" above floor	Wall/ceiling labeled for use
Battery standby	24 hr + 5 min alarm (15 min voice evac)	Multiply by 1.25 for margin
NAC voltage drop	End-of-line ≥ device minimum (16V)	Use voltage drop formula; recalc for long circuits
Record retention	Next test + 1 year	Keep on-site for AHJ
Ground fault trouble	Annunciate in ≤200s	Panel should indicate which circuit

• Formula: NAC Voltage Drop
  V_{drop} = 2 × L × I × R_{cable}/1000
  Where L = length (ft), I = current (A), R_cable = ohms/1000ft (see wire table)
• Battery Sizing
  • Total Standby Load (A) × 24 hr + Total Alarm Load (A) × 5/60 hr = Amp-hours
  • Multiply by 1.25 for margin; round up to next standard battery size
• “If in doubt, test and document!” – Always log all findings, even if ‘passed.’
• Always label device addresses at device and on plan drawings.