The who, what, where and why of waking to fire alarms: a review

Abstract

This review brings together several different strands of research: (i) The sleep arousal literature pertaining to auditory arousal thresholds (AAT), (ii) studies on factors affecting responsiveness to auditory signals during sleep, (iii) literature on responsiveness to smoke detector alarms during sleep and (iv) research on fire fatality statistics and victim characteristics. The review discusses the influence of age, sleep deprivation, signal frequency, background noise, hearing loss, time of night, stage of sleep, sex differences, dream incorporation, depression, signal meaningfulness, sleeping tablets, alcohol and marijuana on responsiveness during sleep. Studies using smoke alarms clearly suggest that an unimpaired sleeping adult will awaken quickly to a 55-60 dBA alarm (such as with a hallway installation), while the AAT literature suggests higher thresholds (most likely due to differences in signal frequency). However, it is argued that the level required to wake such adults under the ideal circumstances of an experimental situation should not be the minimum standard for pillow audibility. Such a level is unlikely to arouse children, those on sleep inducing medication, people with high frequency hearing loss (as may occur with age), those who are sleep deprived or those under the influence of alcohol or marijuana. The responsiveness of the unimpaired adults tested is not generalisable to the responsiveness of the people most likely to be the victims of fire occurring while they are asleep (the very young, elderly, intoxicated, or sick). The sound intensity of the alarm at the pillow should have the highest chance of arousing those most at risk of dying. It is therefore recommended that smoke detector alarms be installed in the bedrooms themselves such that the signal intensity is at the maximum level tolerable to the human ear, that is approximately 90 dBA. noted that 81% of the fatal fires were at night (8pm to 8am) and in those 86% of victims were sleeping. Moreover, in fires during the day, 31% of the victims were actually sleeping. Thus being asleep is a much stronger risk factor for dying in a fire than time of day. Three quarters of those who were asleep did not move from the room in which they were originally located, suggesting that waking either did not occur or occurred too late to allow escape.Many countries have legislated for mandatory installation of smoke detectors in homes and in Australia the standard installation is in the hallway. Assuming they are in working order, how likely is it that a smoke detector will arouse a sleeper quickly? It would seem that the intensity of the alarm at the pillow is important in determining responsiveness, but how does the importance of this factor compare to other variables?What are the most salient risk factors that will determine whether an individual will awaken or not? If we know these risk factors how can we use this information in a practical way to reduce fire fatality risk? The following review sets out to provide answers where these may be...

Comparison of the Effectiveness of Different Fire Notification Signals in Sleeping Older Adults

“…Firstly, the modified methods of limits methodology meant that each volume level of a signal was not presented from silence, as would be the case when a smoke alarm signal sounds. Examination of the literature on awakenings to alarms [4,5] suggests that people may have lower AATs (i.e. wake up more readily at a certain decibel level) when that sound cuts in from silence.…”

“…It seems that sleep in ''normal'' populations is not in itself the major risk factor for fire fatality but that additional risk factors need to be present to substantially increase the chance of sleeping through an alarm. Studies of smoke alarms, auditory arousal and sleep [4] tells us that significant risk factors include being a child, being under the influence of hypnotics, being alcohol intoxicated, being hearing impaired, being sleep deprived and having high levels of background noise.…”

Optimizing Emergency Awakening to Audible Smoke Alarms: An Update

“…In order to estimate the percentage of those aged 60 to 69 years who would not awaken to a hallway high-pitched alarm (55-60 dBA alarm of 2000-4000Hz), Bruck (2001) extrapolated from ISO 7029-1984 data (International Organisation for Standardisation, 1984) on hearing threshold values. Using a derived 41-dBA difference between awake and asleep thresholds, it was estimated that at least 25% of people in their 60s would not awaken to such a hallway alarm.…”

Sleep And Fire: Who Is At Risk And Can The Risk Be Reduced?

“…Among the 6-64 yr olds 65% had ingested alcohol at the time of their death and of these, 40% were asleep. Secondary analyses of this data [6], based on some assumptions, concluded that among those that were asleep perhaps only about a quarter were asleep, able bodied and unimpaired (see Fig. 2).…”

“…There is a considerable literature on sleep and arousal in different circumstances and studies in this area have been extensively reviewed previously [6,16]. This paper will mainly focus on those studies that have used fire cues or alarm signals to investigate awakening.…”