Code Reference
Fire ProtectionNFPA 72 2022

Section 18.4.5/Audible Notification Appliance Requirements

NFPA 72 Section 18.4.5 covers audible alarm requirements including the 15 dB above ambient rule and temporal-3 pattern.

What this section requires

Audible notification appliances must produce a sound level at least 15 dB above the average ambient sound level or 5 dB above the maximum sound level lasting at least 60 seconds, whichever is greater. The minimum sound level is 75 dBA at the device. In sleeping areas, the alarm must produce 75 dBA at the pillow. The fire alarm signal must use the temporal-3 pattern (three pulses followed by a pause) per the ANSI standard for evacuation signals.

Why this section exists

An audible alarm that cannot be heard above background noise fails to notify occupants. The 15 dB above ambient requirement ensures the alarm is clearly distinguishable from normal building sounds. The temporal-3 pattern provides a standardized signal that occupants can recognize as an evacuation alarm regardless of the building they are in. The sleeping area requirement addresses the higher threshold needed to wake sleeping occupants.

What plan reviewers look for

Plan reviewers check that audible notification appliances are located throughout the building to achieve the required sound levels. They verify the appliance sound output rating against the expected ambient noise levels in each area. For sleeping areas, they check that the 75 dBA at pillow requirement is addressed in the design.

Common violations

Insufficient coverage in noisy spaces
Mechanical rooms, kitchen areas, or manufacturing spaces have high ambient noise levels but the same audible appliances as quiet office areas. Higher-output appliances or additional devices are needed to achieve the 15 dB above ambient requirement.
Sleeping area sound level not addressed
Hotel rooms or dormitory rooms do not have dedicated audible appliances or do not demonstrate that 75 dBA is achieved at pillow level with the door closed.
Non-standard alarm signal pattern
The fire alarm system uses a steady or non-temporal signal pattern instead of the required temporal-3 evacuation pattern.
Compliance tip
Document the expected ambient noise level for each area type (office, mechanical, sleeping) and verify that the specified appliance output achieves 15 dB above ambient. Specify temporal-3 pattern in the fire alarm specifications. For sleeping areas, show the calculation or test methodology for achieving 75 dBA at pillow level.

Related NFPA 72 requirements

Section 18.4.3 covers visible notification appliance placement. Section 18.4.8 covers textual audible appliances (voice evacuation). Section 18.5 covers the performance criteria for all notification appliances.

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Related sections

7.10.1Exit Marking and SignageNFPA 10117.5.3Smoke Detector SpacingNFPA 72 202218.5.3Visible Notification Appliance PlacementNFPA 72 2022