Home Smoke Alarm Technologies

Studies show that nearly all U.S. homes have at least one smoke alarm. National fire statistics show that forty percent of all home fire deaths occur in homes with no smoke alarms, and that 23% of fire deaths (660 deaths per year, on average) occur in homes where a smoke alarm was present but did not operate¹.  When smoke alarms fail to operate, it is usually because batteries are missing, disconnected or dead².  Research has shown that people who remove or disconnect the batteries in their smoke alarms often do so because of nuisance alarm activations. 

The sensors used in home smoke alarms today are improved versions of sensors developed more than 40 years ago.  Over the last 10 - 15 years, there have been significant advances in microelectronics, sensors and other technologies that could potentially be used to improve home smoke alarms.  The U.S. Fire Administration, in partnership with the Consumer Product Safety Commission and Oak Ridge National Laboratory, is looking into technologies that could be used to improve home smoke alarms.  This work has several distinct elements:

• A look at different types of sensors that could be used in home smoke alarms.  Emphasis is placed on new or evolving technologies that promise better performance. 
• Development of new signal processing techniques to combine the output from multiple sensors that will likely be part of the next generation of home smoke alarms.
• Review of sounder technologies that can produce a lower-frequency alert sound that recent research has shown to be more effective at awakening sleeping children and older adults. 

A report on the first phase of this ongoing research can be downloaded from the website of Oak Ridge National Laboratory:  Home Smoke Alarms - A Technology Roadmap (PDF, 1.1 Mb).

The key findings of this first phase of the project include:

• A significant improvement in smoke alarm performance is possible if more than one sensor is used to make the decision about what is an alarm condition versus what is a nuisance condition.  
• Inexpensive microcontrollers can allow advanced signal processing, from single or multiple sensors, to discriminate between fire and nuisance sources and to provide earlier detection.
• Carbon monoxide sensors can serve a dual role of serving as a sensor for fire detection as well as providing an alarm for the presence of excessive carbon monoxide (CO).
• Temperature sensors can act in concert with other sensors to authenticate flaming fires.
• Photoelectric sensors can be improved by using blue light sources and by using dual-angle scattering.
• Material-based sensors, such as heated-metal-oxide or Taguchi sensors, can be very sensitive to fire effluents, but they suffer from interference of other sources and degradation that cannot be easily checked.
• Physical-based sensors, such as nondispersive infrared (NDIR) sensors, can be designed to detect principal combustion products and to be self-checking, but inexpensive versions are not presently available.
• Linear discriminate analysis is a mathematical technique that can be implemented to optimizing signal processing to better distinguish between conditions that warrant alarm and those that do not.

1. Ahrens, Marty, “Home Smoke Alarms: The Data as Context for Decision,” Fire Technology, 44, 313–327, National Fire Protection Association, 1 Batterymarch Park, Quincy, MA 02169-7471, 2008
2. Ahrens, Marty, “Smoke Alarms in U.S. Home Fires,” National Fire Protection Association, 1 Batterymarch Park, Quincy, MA 02169-7471, September 2009.