Wireless Smoke and Fire Alarms

Although significant progress has been made in the United States in reducing the number of deaths caused by accidental fires in the home, these incidents still kill more than 3,000 individuals each year.  Better education about the dangers of fire and wider use of smoke alarms are generally credited with reducing the total number of fatalities associated with accidental fires in the home, but experts agree a number of obstacles prevent that total from being reduced further.

Recent research indicates that certain populations (the elderly, those with impaired hearing) have difficulty hearing conventional smoke alarm frequencies.   Additional research indicates that small children may sleep too soundly to wake to the sound of these alarms.   A fire that starts near these individuals may prove fatal – either because the victims do not hear the alarm, or because those who are able to respond to the alarm are located too far away to hear it promptly and act quickly.

Currently, the U.S. Consumer Product Safety Commission (CPSC) recommends installing a smoke alarm on every level of the home.  The National Fire Protection Association (NFPA) urges that alarms be installed on every level of the home and outside all sleeping areas.    NFPA further recommends installing smoke alarms in every room where people sleep.

These guidelines go far to protect families, but may not effectively address the issues described above.  Most significantly, independently operating smoke alarms only sound when the units are directly exposed to smoke.  Other units in the home may not sound until smoke concentrations have reached lethal levels.   The chance to reach sound sleepers or hearing-impaired occupants nearest the fire’s origin may pass before other family members hear the alarm.

To address this problem, since 1993, building codes have required that all new homes include hardwired smoke alarm systems, connected to the home’s electrical system.  (Since 1996, codes have required these systems to include battery backup protection so that the units will operate during power outages.) In homes with these systems, when one smoke alarm sounds, all the alarms sound, thus increasing the amount of time to escape from a fire and/or reach those who may not hear the alarm.

Despite these new regulations, an estimated 90 million homes – those built before 1993 – remain without the protection of wireless interconnected smoke alarm systems.  Retrofitting these homes is possible, but involves rewiring and other expense.  A new solution, wireless interconnected smoke alarm systems, is on the verge of commercialization.

What the Research Reveals
A number of studies have examined the potential effectiveness of these wireless smoke alarm systems.  Here is a summary of what recent research has concluded:

A Review of the Sound Effectiveness of Residential Smoke Alarms, U.S. Consumer Products Safety Commission, December 2004 — In 2003, CPCS undertook a study to look specifically at how effective smoke alarms are in waking older adults.  The study was subsequently broadened to look at whether smoke alarms are effective in waking children.  The agency found:

• Voice and low frequency alarms may be more reliable in waking children under the age of 16, who may sleep more deeply than adults.
• Currently available smoke alarms may not wake older adults with impaired hearing.
• Depending on where they are placed in the home, the sound emitted by smoke alarms may not transmit effectively throughout the home due to walls, closed doors and other barriers.
• Placing interconnected smoke alarms in bedrooms may help warn the occupants of smoke and fire dangers when bedroom doors are shut.
• The industry needs to examine the feasibility of providing different (new) warning systems and sounds in order to accommodate the many variables presented by today’s homes and the various needs of those who occupy them.

Most important, the study concluded, wireless interconnected alarms can provide earlier warning of smoke and fire.   With earlier warning, occupants have more time to act, and a better chance to escape.

U.S. Experience with Smoke Alarms and other Fire Protection/Alarm Equipment, National Fire Protection Association, November 2004 —

NFPA estimates that U.S. home fire deaths could be reduced by more than 1,000 each year if all homes had working smoke alarms.  This study examines some of the ways that goal might be achieved.  Among NFPA’s conclusions:

• The presence of smoke alarms appears to help residents control small fires better.  That is, four out of every ten fires reported to fire departments occur in the small number of homes without smoke alarms.
• When fires are reported to the fire department, the rate of death resulting from the fires is higher in homes without smoke alarms.
• Residents may not hear individual smoke alarms that are not interconnected to other units when they are on other floors of the house or in other rooms separated by a closed door – the possibility of wider use of interconnected smoke alarms is another opportunity for further improvement in home smoke alarm protection.
• As to the problem of children not waking to smoke alarms, Interconnected smoke alarms, with an alarm that would sound in each bedroom in response to a fire anywhere in the home, would address many of these concerns by increasing the proximity to a sounding device.
• Escape time increases when additional smoke alarms are installed in bedrooms. (Most residential fires occur at night.)

And finally, the report notes, Wireless smoke alarm technology that uses radio frequency as a means to interconnect battery powered smoke alarms is being tested.  Costs have fallen for many types of technical equipment.  Should this prove true for these smoke alarms, it would offer the potential advantages of interconnectivity with less expense and installation effort than with traditional hard-wired smoke alarms and allow the alarm to sound throughout the home.

In addition, the following looked various aspects of human response to smoke alarm signals:

• The Effectiveness of Different Alarms in Waking Sleeping Children, Dorothy Bruck, Sharnie Reid, Jefoon Kouzma and Michelle Ball, School of Psychology, Victoria University, Melbourne.
• The Effect of Alcohol upon Response to Fire Alarm Signals in Sleeping Young Adults, Michelle Ball and Dorothy Bruck, School of Psychology, Victoria University, Melbourne.

Among the conclusions:

• Many children ages 6 to 15 sleep too deeply to hear traditional smoke alarms.  Alarms that employ a recorded voice or low pitch signal may be more effective in waking these groups.
• Those impaired by alcohol also may respond more effectively to lower pitched alarms or to alarms with a recorded female voice.

The Wireless Option
New wireless interconnected smoke alarm systems are in development to address the concerns described above.  Those systems will include multiple smoke alarms that can be located throughout the home, then connected via radio frequency so all alarms sound when one alarm sounds.  Add-on units will be available to communicate with high-risk family members (children and those with hearing problems). Features/benefits of these new systems will include:

• Ability to retrofit older homes with an interconnected system without the need for expensive rewiring.
• Ability to provide early warning of fire no matter where in the home the fire originates.
• Extra time to reach children and the hearing impaired who may not hear an alarm.
• Modified units to provide customized warning to children and the hearing impaired.
• Ability to expand hard-wired systems to increase the level of fire protection.
• Extra protection in situations where one alarm in the home has dead or missing batteries.
• And, MOST IMPORTANT, more time to escape when fire strikes.

Sources:

1. NFPA Online, Smoke Alarm Fact Sheet
2. A Review of the Sound Effectiveness of Residential Smoke Alarms, U.S Consumer Product Safety Commission, CPSC-ES-0502, December 2004.
3. CPSC, 2004.
4. Your Home Fire Safety Checklist, U.S. Consumer Product Commission, date TBD.
5. Smoke Alarms, National Fire Protection Association fact sheet, http://www.nfpa.org (Learning/Public Education/Fact Sheets/Fire Protection Equipment)