What devices are required to have an internal sound level of at least 15 dBA above the average ambient sound level?

Audible alarm notification appliances are required to have an internal sound level of at least 15 dBA above the average ambient sound level to ensure that they can effectively alert occupants in a building to a fire emergency. This sound level requirement is essential because it enhances the likelihood that individuals will perceive the alarm over background noises, which may vary depending on the environment, such as in commercial spaces with ongoing operations, machinery, or conversations.

If the sound level of the alarm is not sufficiently above the ambient noise, it may go unnoticed, potentially delaying evacuation and endangering lives. The National Fire Alarm and Signaling Code (NFPA 72) outlines this requirement to maintain a consistent standard for life safety.

Other device types listed, such as visual alarm devices, manual pull stations, and heat detectors, serve different purposes and have different requirements under the code. For instance, visual alarms have their own standards for brightness rather than sound, manual pull stations do not emit sound, and heat detectors are designed to respond to temperature changes rather than providing audible alerts.