Smoke Alarm Signal Research Articles

Age-Dependent Responsiveness to Smoke Alarm Signals Among Children.

Although it has been established that smoke alarms have more difficulty awakening children from sleep than adults, no attempt has been previously made to characterize how smoke alarm responsiveness changes with age during childhood. The objective of this study is to evaluate the age-dependent responsiveness to various smoke alarm signals among children 5 to 12 years old. The effect of age on children's response to 4 types of smoke alarms (human voice, hybrid voice-tone, low-frequency tone, and high-frequency tone) was evaluated using combined data from 3 previous studies. There were 540 subjects (median age 9 years; 51.7% male). The proportion of children who awakened demonstrated a statistically significant (P < .001) increase of 3.1% to 7.6% for each additional year of age between 5 and 12 years old for the 4 alarm types. Similarly, child age showed a statistically significant (P < .001) effect on the proportion who escaped for each of the 4 alarm types. The proportion of subjects who awakened or escaped did not differ significantly by sex for any of the alarm types. Median time-to-awaken and median time-to-escape decreased with increase in child age for all alarm types. This study demonstrates the substantial influence of child age on the effectiveness of audible smoke alarms during childhood. Among 12-year-olds, only 56.3% escaped within 1 minute (and 67.6% within 2 minutes) to a high-frequency tone. However, a hybrid voice-low-frequency tone alarm is >96% effective at awakening and prompting escape within 1 minute among children 9 years and older.

Optimizing Smoke Alarm Signals for Those at Highest Risk for Residential Fire-Related Death: Testing the Effectiveness of Children’s Smoke Alarms for Sleeping Older Adults

Optimizing Smoke Alarm Signals for Those at Highest Risk for Residential Fire-Related Death: Testing the Effectiveness of Children’s Smoke Alarms for Sleeping Older Adults

Optimizing smoke alarm signals: Testing the effectiveness of children\u2019s smoke alarms for sleeping adults

BackgroundBeing asleep is an important risk factor for death during a residential fire; however, the high-frequency tone smoke alarms in many homes will not adequately awaken children who are old enough to self-rescue. In a series of previous studies, we identified smoke alarm signals that effectively awaken children 5–12 years old and prompt their escape. Because it is impractical to have separate alarms for children and adults in a household, the purpose of this study is to test whether alarms that are effective in awakening children and prompting their escape are also effective among adults.MethodsUsing a randomized, non-blinded, repeated measures design, 150 adults 20–49 years old were exposed during stage 4 sleep to four different smoke alarms. Statistical tests included the Kaplan-Meier estimator, generalized Wilcoxon test, and hazard ratios with Wald’s 95% confidence intervals.ResultsThe median age of study subjects was 30.0 years and 67.3% were female. Almost all (n = 149) subjects awakened and performed the escape procedure to all four alarms; one individual did not awaken or escape to the high-frequency tone alarm. The median time-to-awaken was 2.0 s for the high-frequency tone alarm and 1.0 s for the other three alarms. The median time-to-escape for the high-frequency tone alarm was 12.0 s, compared with 10.0 s for the low-frequency tone alarm and 9.0 s each for the female and male voice alarms. All pairwise comparisons between the high-frequency tone alarm and each of the other three alarms were statistically significant for the probability functions for time-to-awaken and time-to-escape. There were no significant differences in these outcome measures between the latter three alarms, except for female voice versus low-frequency tone alarms for time-to-escape.ConclusionsAll alarms performed well, demonstrating that smoke alarms developed for the unique developmental requirements of sleeping children are also effective among sleeping adults. Compared with a high-frequency tone alarm, use of these alarms may reduce residential fire-related injuries and deaths among children, while also successfully alerting adult members of the household.

Do sleeping children respond better to a smoke alarm that uses their mother's voice?

ABSTRACT Objective Being asleep at the time of a residential fire increases fire-related fatality risk. This study tested whether children awaken from slow wave sleep and perform an escape procedure better to a voice smoke alarm that uses their mother's voice compared with a female stranger's voice or a low-frequency tone alarm. Methods Using a randomized, non-blinded, repeated measures design, 176 children 5-12 years old were exposed during stage 4 slow wave sleep to four smoke alarm signals: 1) the voice of the child's mother, 2) the voice of a female stranger, 3) low-frequency 500 Hz square wave tone, and 4) conventional residential high-frequency tone. The alarms were assessed regarding their ability to awaken the children and prompt their performance of an escape procedure. Results Among the 176 subjects, 78.4%, 83.0%, 88.1%, and 49.4% awakened and 78.4%, 81.3%, 85.8%, and 48.3% successfully performed the escape procedure within 5 minutes of alarm onset in response to the mother's voice, stranger's voice, low-frequency tone, and high-frequency tone alarms, respectively; while the median time-to-escape was 23.0, 24.0, 41.5, and >300 seconds for these four alarms, respectively. Conclusions The two voice alarms and low-frequency tone alarm significantly out-performed the high-frequency tone alarm, with the low-frequency tone alarm and female stranger's voice alarm performing best. Compared with the voice of a female stranger, personalizing the alarm message with the voice of the child's mother did not increase alarm effectiveness. These findings provide important information for development of an effective and practical smoke alarm for children.

Do Sleeping Children Respond Better to a Smoke Alarm That Uses Their Mother's Voice?

Being asleep at the time of a residential fire increases fire-related fatality risk. This study tested whether children awaken from slow wave sleep and perform an escape procedure better to a voice smoke alarm that uses their mother's voice compared with a female stranger's voice or a low-frequency tone alarm. Using a randomized, nonblinded, repeated measures design, 176 children 5 to 12 years old were exposed during stage 4 slow wave sleep to 4 smoke alarm signals: 1) the voice of the child's mother, 2) the voice of a female stranger, 3) low-frequency 500 Hz square wave tone, and 4) conventional residential high-frequency tone. The alarms were assessed regarding their ability to awaken the children and prompt their performance of an escape procedure. Among the 176 subjects, 78.4%, 83.0%, 88.1%, and 49.4% awakened and 78.4%, 81.3%, 85.8%, and 48.3% successfully performed the escape procedure within 5 minutes of alarm onset in response to the mother's voice, stranger's voice, low-frequency tone, and high-frequency tone alarms, respectively; while the median time-to-escape was 23.0, 24.0, 41.5, and >300 seconds for these 4 alarms, respectively. The 2 voice alarms and low-frequency tone alarm significantly outperformed the high-frequency tone alarm, with the low-frequency tone alarm and female stranger's voice alarm performing best. Compared with the voice of a female stranger, personalizing the alarm message with the voice of the child's mother did not increase alarm effectiveness. These findings provide important information for development of an effective and practical smoke alarm for children.

Analyzing smoke alarm response to flaming fires using the fire model JET

An algorithm that calculates the time dependent smoke concentration in a fire-induced ceiling jet within a smoke layer and algorithms for predicting the response of photoelectric smoke alarms, both of which are part of the computer model JET, are examined using three different fires in a small room. The objectives of this analysis are to test the ceiling jet smoke algorithm and understand the limitations of analyzing signals from photoelectric smoke alarms located in the ceiling jet to estimate fire size and thereby support decision making by emergency responders. The analysis is restricted to flaming fires that produce turbulent plumes and can be represented by axisymmetric point sources. Two different smoke yields from the literature are used to obtain ceiling jet smoke density from JET. Depending on the value of the smoke yield used, the predictions of JET follow or do not follow the photoelectric smoke alarm signals. This suggests that additional information about how smoke yields are measured or that a better calibration technique is required in order to accurately model smoke alarm response.

How does the pitch and pattern of a signal affect auditory arousal thresholds?

How arousal thresholds vary with different sounds is a critical issue for emergency awakenings, especially as sleepers are dying in fires despite having a working smoke alarm. Previous research shows that the current high-pitched (3000+ Hz) smoke alarm signal is significantly less effective than an alternative signal, the 520 Hz square wave, in all populations tested. However, as the number of sounds tested has been small further research is needed. Here we measured auditory arousal thresholds (AATs) across signals with a range of characteristics to determine the most effective waking signal. Thirty-nine young adults participated over three nights. In Part A, nine signals were presented in stage 4 sleep with ascending decibel levels. Signals were short beeps in the low- to mid-frequency range with different spectral complexities: square waves, pure tones, whoops and white noise. Part B manipulated temporal patterns, inserting silences of 0, 10 and 21 s after each 12 s of beeps. It was found that the low-frequency (400 and 520 Hz) square waves yielded significantly lower AATs than the alternatives. A trend was found across the three temporal manipulations, with a 10 s intervening silence showing some advantage. These findings support earlier research indicating that the best sound for awakening from deep sleep is a low-frequency square wave. It is argued that the signal with the lowest response threshold when awake may be the same as the most arousing signal when asleep, especially where the sleeper processes the signal as meaningful.

Smoke Alarms for Sleeping Adults Who are Hard-of-Hearing: Comparison of Auditory, Visual, and Tactile Signals

People who are hard-of-hearing may rely on auditory, visual, or tactile alarms in a fire emergency, and US standards require strobe lights in hotel bedrooms to provide emergency notification for people with hearing loss. This is the first study to compare the waking effectiveness of a variety of auditory (beeps), tactile (bed and pillow shakers), and visual (strobe lights) signals at a range of intensities. Three auditory signals, a bed shaker, a pillow shaker, and strobe lights were presented to 38 adults (aged 18 to 80 yr) with mild to moderately severe hearing loss of 25 to 70 dB (in both ears), during slow-wave sleep (deep sleep). Two of the auditory signals were selected on the basis that they had the lowest auditory thresholds when awake (from a range of eight signals). The third auditory signal was the current 3100-Hz smoke alarm. All auditory signals were tested below, at, and above the decibel level prescribed by the applicable standard for bedrooms (75 dBA). In the case of bed and pillow shakers intensities below, at, and above the level as purchased were tested. For strobe lights three levels were used, all of which were above the applicable standard. The intensity level at which participants awoke was identified by electroencephalograph monitoring. The most effective signal was a 520-Hz square wave auditory signal, waking 92% at 75 dBA, compared with 56% waking to the 75 dBA high-pitched alarm. Bed and pillow shakers awoke 80 to 84% at the intensity level as purchased. The strobe lights awoke only 27% at an intensity above the US standard. Nonparametric analyses confirmed that the 520-Hz square wave signal was significantly more effective than the current smoke alarm and the strobe lights in waking this population. A low-frequency square wave signal has now been found to be significantly more effective than all tested alternatives in a number of populations (hard-of-hearing, children, older adults, young adults, alcohol impaired) and should be adopted across the whole population as the normal smoke alarm signal. Strobe lights, even at high intensities, are ineffective in reliably waking people with mild to moderate hearing loss.

Strobe lights versus auditory smoke alarm signals: Effectiveness for waking up selected populations

Strobe lights are recommended in the USA and elsewhere as a suitable emergency notification signal for waking the deafor hard ofhearing (NFPA 72, 2002 standard). This paper reviews the relevant literature, and reports on the waking effectiveness of strobe lights (177 candela or more) in comparison to the current high pitched smoke alarm and a low frequency square wave tone (520 Hz dominant frequency). The signals were activated at increasing intensity levels during slow wave (deep) sleep in two groups: (i) 38 adults aged 18–77 years with mild to moderately severe hearing loss in the range of 25–70dBA in both ears, and (ii) 32 young adults aged 18–26 years impaired with alcohol at 0.05 blood alcohol content. It was found that three quarters ofthe participants slept through the strobe light activated at above the recommended intensity of the standard. Further, adding a strobe light to a current smoke alarm signal is likely to be less effective at waking participants than sounding a low frequency square wave...

Awakening of Sleeping People: A Decade of Research

The results of over a decade of research at Victoria University on the effectiveness of various smoke alarm signals for awakening sleeping people are presented and compared. The results show that the signal level (sound volume, light intensity, etc.) and the type of sound or signal affect the probability of people being woken up by an alarm. The 520 Hz square wave sound was the most effective of the sounds tested, waking most (often all) of the participants. The smoke alarms currently used in Australia and the USA emit sounds of about 3,100 Hz. Many participants did not wake up to such tones even when very loud at the pillow (95 dBA). In all groups tested the high-pitched sound was the worst and in most, notably children, young adults (sober and 0.05 BAC) and older adults, it was much worse than the 520 Hz square wave signal. In adults with hearing loss it was more than seven times as effective as the current signal and more effective than the bed and pillow shakers. Strobe lights were found to have very poor waking effectiveness. A voice alarm was quite effective for younger age groups but not for older adults. The voice alarm was also found to have real problems in waking participants with limited English. It is recommended that the 520 Hz square wave sound in the T-3 pattern be adopted as a replacement for the current smoke alarm sound.

Towards a better smoke alarm signal - an evidence based approach

This paper focuses on experimental findings on the waking effectiveness of different auditory signals in children, deep sleeping young adults, older adults, the hard of hearing and the alcohol impaired. Wherever possible, data is graphically presented in terms of the percentage sleeping through different sounds at 75 dBA. It includes previously unpublished data comparing the waking effectiveness of various signals in young adults who were either sober or moderately impaired with alcohol. A summary of the evidence concerning the best and worst signal shows that the 520 Hz square wave signal is at least 4 to 12 times more effective than the current high pitched signal in the populations tested. Research supporting lower frequency signals and mixed frequency signals as being the best alarms for people when awake is also discussed. It is argued that the 520 Hz square wave signal, which has been tested now in six different experimental studies, has a sufficient evidence base to warrant the recommendation for its widespread introduction as a new smoke alarm signal for the whole population. Not improving the alarm signal is likely to result in fatalities and injuries that may have been avoidable.

Strobe Lights, Pillow Shakers and Bed Shakers as Smoke Alarm Signals

This paper assesses the waking effectiveness of strobe lights and pillow and bed shakers as smoke alarm warning devices and compares them to an auditory signal. The signals were activated at increasing intensity levels during slow wave (deep) sleep in two groups, (i) 38 adults aged 18-77 years with hearing loss of 25- 70 dBA in both ears, and (ii) 32 young adults aged 18 -26 years impaired with alcohol at 0.05 blood alcohol content. Three quarters of both groups slept through the strobe light activated at above the intensity required by the standard whereas a 75 dBA 520 Hz square wave T-3 sound woke over 90%, and at a louder volume 100%. The pillow and bed shakers did not wake 17-20% of the hard of hearing participants at the intensity level as purchased. Hard of hearing participants aged ≥60 years were less likely to wake up to the bed shaker than those aged <60 years. The pillow and bed shakers tested were not an effective means of waking moderately alcohol impaired young adults from deep sleep, with 36%-42% not waking up at the intensity level as purchased. For both groups the pillow and bed shakers were less effective than the 520 Hz square wave T-3 sound at 75 dBA at the pillow. This study supports earlier research showing that when sleep stage is assessed strobe lights have poor waking effectiveness. The 520 Hz square wave sound was more effective than the non-auditory signals for both groups

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

No previous research has investigated the responsiveness of older adults (65–85 years) to different emergency fire signals during sleep. In this study the auditory arousal thresholds (AAT) of 45 older adults were compared across four signals; the high pitched T-3 (as in current US smoke alarms), a mixed frequency T-3 (500–2500 Hz), a 500 Hz T-3 and a male voice. Participants were carefully screened, including for hearing, and awoken from deep sleep in a repeated measures design. Sounds increased progressively in volume until awakening occurred. It was found that the median AAT for the most effective signal, the mixed frequency T-3, was 20 dBA lower than the median AAT of the least effective signal, the current US high frequency smoke alarm signal. This finding is consistent with previous research, where the high pitched signal required a significantly louder volume than alternatives to wake sleepers of different ages, including children. Those aged over 75 years are especially at risk for sleeping through high pitched signals, probably due to the normal age-related decline in the ability to hear high pitched sounds. The minimum pillow volume of 75 dBA is inadequate for those over 75 years if a 3000 Hz notification signal is used. It is recommended that the high frequency signal currently found in smoke alarms be replaced by an alternative signal that performs significantly better in awakening most of the adult population, once the nature of the best signal has been determined.

Optimizing Emergency Awakening to Audible Smoke Alarms: An Update

This review examines research on arousal from sleep in an emergency. It considers whether the current smoke alarm signal is optimal for waking those most at risk of dying in a fire and, if not, how it may be improved. The fire fatality rate during the sleeping period is approximately three times greater than at other times. Four key areas are reviewed: (a) the characteristics of four signals (high-frequency beeping, Temporal 3, voice, and naturalistic sounds); (b) how human characteristics alter arousal to different signals; (c) research comparing the effectiveness of different alarms in different sleeping populations; and (d) acoustical, methodological, and theoretical implications. Significant risk factors for staying asleep include high levels of background noise, being a heavy sleeper, sleep deprivation, being a child, hypnotics, alcohol intoxication, and hearing impairment. The high-frequency beeping signal was significantly less effective than either a voice alarm or mixed-frequency beeping in waking selected at-risk groups. The alternative signals were more effective in arousing various groups of sleepers than was the high-frequency signal currently used in smoke alarms. Replacement of the current smoke alarm signal with one of a lower frequency is likely to wake more people more quickly and save lives.

Audible performance of smoke alarm sounds

This paper concerns a study aimed at selection of alarm sounds with improved audible performance characteristics for older listeners over current conventional residential smoke detectors. Many current residential smoke detectors possess alarms that have their primary frequency peak in the 4000-Hz region of the audible spectrum. Additionally, many of these alarms are constant instead of providing temporal modulation of the signal. This study analyzed a variety of alternative sounds for selection as a better choice for an ‘age-sensitive’ smoke alarm signal. The study presented a battery of candidate sounds to pairs of subjects aged 65 years and older with varying levels of hearing impairment (0–45 dB) in their own homes to see which sounds performed best in terms of detection, localization, and perceived attention-getting value. Subjects were placed in various location- and masking-based conditions within their homes during listening periods and subjected to sounds played at a constant level. A computerized system collected response data as the battery of stimuli was presented. The data showed a fairly predictable positive trend in detection and localization performance level as the frequency of the stimuli decreased from 4000 to 500 Hz. The data also showed that pulsed signals were more detectable than steady alarms.

Audible Performance of Smoke Alarm Sounds

This paper concerns a study aimed at selection of alarm sounds with improved audible performance characteristics for older listeners over current conventional residential smoke detectors. Many current residential smoke detectors possess alarms that have their primary frequency peak in the 4000 Hz region of the audible spectrum. Additionally, many of these alarms are constant instead of providing temporal modulation of the signal. This study analyzed a variety of alternative sounds for selection as a better choice for an “age sensitive” smoke alarm signal. The study presented a battery of candidate sounds to pairs of subjects aged 65 and older with varying levels of hearing impairment (0 to 45 dB) in their own homes to see which sounds performed best in terms of detection, localization, and perceived attention-getting value. Subjects were placed in various location- and masking-based conditions within their homes during listening periods and subjected to sounds played at a constant level. A computerized system collected response data as the battery of stimuli was presented. The data showed a fairly predictable positive trend in detection and localization performance level as the frequency of the stimuli decreased from 4000 Hz to 500 Hz. The data also showed that pulsed signals were more detectable than steady alarms.