Studies commissioned by the Fire Protection Research Foundation have shown that the ability of different segments of the population to be awakened by the sound of a smoke alarm varies widely depending on such factors as age and levels of hearing impairment. Research also determined that a low frequency 520 Hz alarm signal was the most effective at awakening people.


In 2010, NFPA 72 standards were revised to require devices capable of 520 Hz low frequency signaling be installed in sleeping areas in facilities such as hotels, school dormitories, assisted living facilities, and apartment buildings.