Sounding the Alarm: Will You Wake Up When the Fire Alarm Goes Off?
Smoke alarms save lives, but only if they work to alert the people at risk. Not waking up in time is often the cause of fire fatalities. According to studies commissioned by the Fire Protection Research Foundation and the U.S. Fire Administration, many people are more at risk because they don’t wake up readily from standard smoke alarms or strobe lights, including:
- People with hearing loss (especially significant loss above 3000 Hz)
- Older adults
- Children
- Heavy sleepers
70 million* Americans have high-frequency hearing loss. Are you one of them?
High-frequency hearing loss inhibits you from hearing everyday sounds, from consonants such as “S” or “F” to children’s or women’s voices — even a smoke alarm. That's right a smoke alarm.
People with Hearing Loss
Even though most people with hearing loss have more trouble hearing high frequencies than low frequencies, the typical smoke alarm uses a high frequency, 3100 Hz pure tone signal. As a result, smoke alarms are not very effective at waking up the hearing impaired. In the "Waking Effectiveness Study", nearly half of subjects with mild to moderately severe hearing loss slept through code-mandated levels (75 dBA) of the 3100 Hz smoke alarm signal.
If you have a hearing loss, how do you know you will wake up to a 3100 Hz tone smoke alarm? Unfortunately, being able to hear it while awake does not predict whether you will wake up to the same from a deep sleep. (See Section 5.3 of the "Waking Effectiveness Study".) However, the 520 Hz square-wave tone used in the Lifetone HL™ Bedside Fire Alarm and Clock was highly effective at waking participants with mild to moderately severe hearing loss: 92% of the people in the "Waking Effectiveness Study" woke up from deep sleep at or below the benchmark level for the 520 Hz square wave. Only 56% woke up at or below the benchmark level for standard alarms’ 3100 Hz pure tone. (Participants were not under the influence of any alcohol, medication or other sleep-affecting factors.)
Note that some people with severe or fluctuating hearing loss at 500 Hz and higher will not reliably hear and wake up to the 520 Hz square-wave signal alone. Strobe lights were found to be ineffective at waking up more than 70% of the subjects in the "Waking Effectiveness Study". That is why the Lifetone HL™ Bedside Fire Alarm and Clock is designed to work with a bed-shaker that produces strong, intermittent vibration. We recommend that people with moderate or greater hearing loss at 500 Hz and higher test whether the 520 Hz square wave and/or the bed shaker are able to awake them several hours after falling asleep (when deep sleep usually occurs).
Older Adults
People who are 65 years or older are at a higher risk of dying or being injured by fire:
“In 2004, older adults (over 64 years old) represented 12% of the U.S. population but suffered more than 30% of all fire deaths…The relative risk of individuals aged 65 and over dying in a fire is 2.6 times greater than that of the general population. The risk worsens as age increases: the risk is 1.7 for adults aged 65 to 74, but soars to 4.7 for those over age 84…Older males are over 50% more likely to die in fires than older women.”
(From “Fire Risk to Older Adults,” Topical Fire Report Series, Volume 7, Issue 7/February 2008, USFA; http://www.usfa.dhs.gov/downloads/pdf/tfrs/v7i7.pdf)
Older adults are more at risk of dying in a fire, due in part to the greater prevalence of hearing loss among people over 60. In large scale audiological testing of people aged 48 and older in Beaver Dam, Wisconsin, the overall rate of hearing loss was 45.9%. Among people 60 to 69, the rate was 43.8%; for people 70 to 79, the rate was 66% and for people 80 to 92, the rate was 90%. (“Prevalence of Hearing Loss in Beaver Dam, Wisconsin: The Epidemiology of Hearing Loss Study,” Cruickshanks et al, 1998.)
Research published in 2006 conducted with healthy people 65 years and older whose hearing was within the norm for their age at all frequencies found that 95% woke up to a 75 dBA 520 Hz square-wave signal and that, on average, they woke up considerably faster to the 520 Hz square-wave signal (called the mixed T-3 signal in the study) than the 3100 Hz pure tone signal of standard smoke alarms. In contrast, 18% slept through the 3100 Hz tone signal, and the mean response was much slower: 192 seconds, compared to 93 seconds for the 520 Hz square-wave signal. Because fire can envelope an entire dwelling within minutes, every second can mean the difference between life and death. (Bruck, Dorothy and Thomas, Ian and Kritikos, Ada (2006) Investigation of auditory arousal with different alarm signals in sleeping older adults. Project Report. Fire Protection Research Foundation, Victoria, Australia. http://www.nfpa.org/assets/files/PDF/Research/Investigation_of_Auditory_Arousal.pdf)
Children
In one study (Bruck and Bliss, 2000), only 29% of children aged 6 to 10 woke up to a high-pitched smoke alarm at the very loud level of 89 dBA, a level equivalent to a buzz saw, a telephone or even a motorcycle. The 2004 Bruck and Ball study found that the 520 Hz square-wave signal was comparable to a recording of the mother’s voice in waking up 96% and 100% respectively of the children in the study.
Lifetone recommends that families with children practice fire drills regularly to help everyone practice what they should do if a fire erupts in the home. Don’t wait for an emergency to find out if your children can hear your smoke alarm while they are sleeping.
Deep Sleepers
How to best wake deep sleepers has not yet been studied extensively. However, it is known that the 520 Hz square-wave signal was more effective than a high-frequency 75 dBA alarm at waking up sober young adults described as deep sleepers. (Ball and Bruck, 2004) For deep sleepers, Lifetone suggests trying and testing either the 520 Hz square-wave signal by itself or adding the Lifetone bed shaker.
Disclaimer: Some individuals may not wake up to the 520 Hz square-wave and/or the Lifetone bed shaker. Deaf people who have reduced tactile sensitivity due to diabetes, for example, may not be able to wake up to a bed shaker. Other factors such as ingesting strong medication and/or significant quantities of alcohol will negatively affect an individual’s ability to wake up to any device.
*Based on Johns Hopkins study published in Archives of Internal Medicine July 2008, which states 55 million Americans ages 20 to 69 have high-frequency hearing loss; and Cruickshanks et. al. Beaver Dam study published in American Journal of Epidemiology, 1998, which states that 66 percent of people 70 to 79 have high-frequency hearing loss, and 90 percent of people ages 80 to 92 have high-frequency hearing loss.
* “Waking Effectiveness of Alarms for Adults who are Hard of Hearing” and “Waking Effectiveness of Alarms for the Alcohol Impaired” studies, National Fire Protection Association Fire Protection Research Foundation, June & July 2007, http://www.nfpa.org/assets/files//PDF/Research/hardofhearing&alarms.pdf