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 alarms as well as other research. One of the main findings of the Research Foundation 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, . This is in contrast to the requirement for UL 268, , 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.