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DE Fire Alarm study materials
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DE Fire Alarm: Notification Appliances and Audible/Visible Signaling

DE Fire Alarm · Work through your exam, one topic at a time.

All guide sections

Notification Appliances and Audible/Visible Signaling

This domain tests whether occupants actually receive the signal. You must know the sound pressure targets by mode, the low-frequency rule for sleeping areas, and how visible appliance intensity and mounting are selected.

Audible signaling

  • Public mode (occupants expected to evacuate): sound level at least 15 dBA above the ambient, or 5 dBA above the maximum sound level lasting 60 seconds or more, whichever is greater, measured 5 ft above the floor.
  • Private mode (trained staff only): at least 10 dBA above ambient.
  • Sleeping areas: at least 75 dBA at the pillow, or 15 dBA above ambient if that is greater, and low-frequency (520 Hz) alarms are required for sleeping areas where the code or listed design calls for them.
  • Alarm, supervisory, and trouble signals must be audibly distinguishable from each other.

Visible signaling

  • Strobes are rated in candela; select the rating from the table using the greatest straight-line distance from the appliance to the farthest point it must cover. Typical public-mode values: 15 cd up to 20 ft, 30 cd for 20-25 ft, 75 cd for 25-30 ft, 110 cd for 30-35 ft.
  • Private mode permits lower effective intensity than public mode.
  • Wall-mounted visible appliances are installed 80 to 96 in. above finished floor; ceiling-mounted units follow the manufacturer's spacing.
  • Appliances within the same field of view must flash in synchronization, typically 1 to 2 flashes per second.
  • Voice systems must be intelligible in all occupied areas, not merely loud enough.

Worked example

A machine room has a measured ambient of 62 dBA that persists. Public mode requires 62 + 15 = 77 dBA at 5 ft above the floor. A horn rated 85 dB at 10 ft produces about 91 dB at 5 ft (+6 dB per halving of distance). At 20 ft it is about 79 dBA - still compliant. At 40 ft it is about 73 dBA - noncompliant. One appliance in the middle of a 80 ft room therefore fails at the far corners, and the designer must add appliances or use higher-output devices until every point reaches 77 dBA.

Traps

  • Using average ambient instead of maximum ambient with duration.
  • Applying the 15 dBA public-mode rule to a private-mode space (it is 10 dBA).
  • Selecting strobes by room area rather than by the farthest viewing distance.
  • Mounting visible appliances above 96 in. or forgetting synchronization in a corridor.
  • Specifying standard horns instead of 520 Hz devices in sleeping areas.