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Review of audible alarm signal waking effectiveness

Smoke alarm and signaling systems are a proven strategy for reduction of fire fatalities in the general population. However, studies have shown that at risk populations such as the elderly, school age children, alcohol impaired, and those that are hard of hearing do not fully benefit from conventional smoke alarm systems, particularly during sleeping hours. Research has been conducted to develop performance requirements to optimize the waking effectiveness for alarm and signaling systems to meet the needs of these at risk groups. This includes previous research from the Research Foundation on the waking effectiveness of alarms1 as well as other research.

The Foundation study involved several tasks including a risk assessment to estimate the potential impact in lives saved of changes in waking effectiveness of smoke alarms for older adults, quantifying the human behavior aspects of the problem, developing benchmark performance criteria for alarm and signaling systems, and reviewing new and promising technologies that address the performance criteria. One of the main findings of this work is that the 520 Hz T-3 sound was the most effective signal to awaken hard of hearing participants. Other studies have shown the same results for children and other at risk populations.

Performance requirements for a sound pressure level of 85 dBA at 10 feet from the device for single and multiple-station smoke alarms appear in multiple codes and standards, including UL 217, Standard for Smoke Alarms. This is in contrast to the requirement for UL 268, Smoke Detectors for Fire Alarm Systems, listed smoke detectors, which is to emit 75 dBA at the pillow. The 85 dBA specification requires significantly more power, which makes the 520 Hz a particular challenge for alarms operating on a battery/battery backup.

There is a need to review all existing data on this topic to clarify the sound pressure level(s) used in previous research and the background and technical basis for the required sound pressure levels in the codes and standards to determine if a lower sound pressure level could provide equivalent alerting when using a 520 Hz frequency.

Research goal: Determine if the performance requirement for sound pressure level can be reduced when using a 520 Hz frequency and still provide equivalent alerting.

1Bruck, Dorothy and Thomas, Ian. Optimizing Fire Alarm Notification for High Risk Groups Research Project. Fire Protection Research Foundation, Quincy, MA. 2007.

Download the project summary. (PDF)

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