Study Shows Millions of People Can't Hear Smoke Alarms
One of the scariest scenarios you can imagine if you suffer from hearing loss is not being able to wake up in the case of a fire.
That is indeed a scary thought and, unfortunately, it happens much too often. The Hearing Loss Association of America (HLAA) has long suspected that people died in fires because they were unable to hear smoke alarms. Until recently, however, no government investigations into the fire fatalities have focused on whether the victims were hearing-impaired, and no smoke alarms or strobe lights were tested to see whether they were effective for people with hearing disabilities.
A recent study by the Fire Protection Research Foundation (FPRF), a nonprofit organization which provides practical data on fire and building safety, finally shed some light and sounded a loud alarm on the failure of most commonly used systems to awake millions of hard-of-hearing people.
This study shows there is a critical need for emergency warning systems to be redesigned or supplemented as soon as technically feasible, says Terry Portis, HLAA's executive director.
Saving Lives, But Not Enough
There is no doubt that well-maintained smoke alarms, which sense the presence of smoke in a room or a building and warn occupants of the impending danger, prevent injuries and save thousands of lives each year. The National Fire Protection Association says these alarms are largely responsible for the nearly 50 percent drop in fire-related deaths in the past three decades.
Invented in the late 1960s, smoke detectors became widely available in the early 1970s. Before that date, fatalities from home fires averaged 10,000 a year, dropping by almost half by the 1990s. That may have been the reason why in 1992, readers of the R&D Magazine, which reports on the newsworthy research and development topics, selected home smoke alarms as one of the "30 Products that Changed Our Lives."
Most conventional smoke alarms feature one of two kinds of detectors. The photoelectric one, which uses light technology and sensors, quickly reacts to smoldering fires that release relatively large amounts of smoke.
The other type, used in the vast majority of American homes, has ionization detectors that work off an electrical current.
Unfortunately, in too many cases neither of these alarms is loud enough to be heard by people with hearing loss, putting an estimated 34 million Americans at risk.
Sleeping Through Fires
According to the July 2007 FPRF study, Waking Effectiveness of Alarms for Adults Who Are Hard of Hearing, the most effective way to wake a sleeping person suffering from mild to moderately severe hearing loss is by emitting a sound he or she can clearly hear.
That might sound like a logical conclusion, but the reality is different. The study -- which also tested various alarms that did not rely on sound emission, such as bed and pillow shakers and strobe lights -- found that the lower pitch tone was considerably more effective than higher pitches (typically 3150 Hz) commonly used in smoke detectors.
In fact, the high signal emitted by conventional smoke alarms failed to awaken up to 43 percent of tested subjects. Bed and pillow shakers woke up over 80 percent of study's participants but strobe lights had the highest failure rate, waking up only 27 percent of those tested. In contrast, a specific audible multiple frequency signal of a 520 Hz square wave -- the signal containing multiple harmonics of the fundamental 520 Hz frequency -- successfully alerted over 90 percent of participants when used at the code-minimum sound level of 75 decibels for 30 seconds. The same device awakened all the subjects when increased to 95 decibels at the pillow.
The Knowledge Gleaned
So is there a full-proof way of ensuring that people with hearing loss can wake up to the sound of a smoke detector?
Not at this time, but knowing what doesn't work is the first important step toward exploring effective solutions.
While currently there are no smoke alarms on the market that emit a low frequency, the study might nudge manufacturers of these systems as well as other warning devices such as carbon monoxide alarms and weather radios to produce safety appliances providing a low frequency near 500 Hz
Finding that an auditory signal at a low pitch is best for alerting those with mild to moderately high hearing loss will certainly prompt further investigation into this area, says FPRF executive director Kathleen Almand. Ultimately it will lead to better protection for this high-risk group.
Knowing Your Rights Can Save Lives
While waiting for more efficient smoke detectors to be available, what can you do to ensure that you or a loved one with hearing loss is well protected in case of a fire?
The first thing to know is your rights. Under the Americans with Disabilities Act, hotels, motels, and other public facilities offering sleeping accommodations are required to provide effective access to the buildings alarm system for hearing-impaired or disabled guests.
If that service is lacking or missing, you can file a complaint at www.ada.gov.
Hopefully it won't be long before fire-related fatalities among hearing-impaired people will be phased out. At least now the warning alarm has been sounded and heard.