The body of scientific knowledge about fire, smoke and smoke detection has developed over many years and is extensive. The USFA has either fully or partially funded a number of research efforts, including a recent study by the National Institute of Standards and Technology’s (NIST) Center for Fire Research. Other contributors to this knowledge include the Consumer Product Safety Commission (CPSC), the National Fire Protection Association, Underwriters Laboratories, the Home Fire Safety Council, the Residential Fire Safety Institute, the Home Fire Sprinkler Coalition, and distinguished academics with expertise in smoke alarm and sensor technology. The body of research reflects the following:
- There are two types of smoke alarms in general use for home smoke alarms: photoelectric and ionization. These smoke alarms sense the presence of smoke differently.
- The type of smoke produced by a fire depends on the type of fire. Flaming fires produce a different type of smoke than smoldering fires.
- Both smoke alarms will detect the smoke from either a smoldering fire or a flaming fire. It has been established and well known for many years that:
- Ionization smoke alarms tend to respond faster to the smoke produced by flaming fires than photoelectric smoke alarms.
- Photoelectric smoke alarms tend to respond faster to the smoke produced by smoldering fires than ionization smoke alarms.
- In some full-scale fire tests, the difference in the time to alarm between ionization and photoelectric smoke alarms was found to be trivial. In other full-scale fire tests, the difference in response time was considerable.
Based on this information, the USFA provides the following guidance to the public and to state and local legislative bodies that may be grappling with the issue of the proper type of smoke alarm to select for use in a residence:
- We cannot state that one type of alarm is better than another because every fire is different.
- Because both ionization and photoelectric smoke alarms are better at detecting distinctly different yet potentially fatal fires, and because no one can predict what type of fire might start in a home, the USFA recommends that every home and place where people sleep be equipped with either (a) both ionization and photoelectric smoke alarms, or (b) dual sensor smoke alarms (which contain both ionization and photoelectric smoke sensors).
- The location of a smoke alarm within a home may be more important than the type of smoke alarm present, depending on the location of a fire. The USFA recommends that users follow the manufacturer’s guidance on the recommended location of smoke alarms in a home.