A Message from the U.S. Fire Administrator about Home Smoke Alarms
Posted on August 27, 2008 by Gregory B. Cade, U.S. Fire Administrator

USFA is aware that there is a growing controversy about which type of smoke
alarm is most appropriate to protect Americans in their homes. In
accordance with our mission to reduce life and economic losses due to fire,
we offer the following guidance regarding home smoke alarms.

USFA recommends that every residence and place where people sleep be
equipped with either both ionization and photoelectric smoke alarms or dual
sensor smoke alarms.

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 residential smoke
alarms: photoelectric and ionization. These types of smoke alarms sense the
presence of smoke differently.
The type of smoke produced by a fire depends strongly on the type of fire.
Flaming fires produce a different type of smoke than smoldering fires.

Both types of smoke alarms will detect the smoke from either a smoldering
fire or a flaming fire. It has been factually established and well known
for many years that:
Ionization type smoke alarms tend to respond faster to the smoke produced
by flaming fires than photoelectric type smoke alarms, and
Photoelectric type smoke alarms tend to respond faster to the smoke
produced by smoldering fires than ionization type smoke alarms.
In some full-scale fire tests, the difference in the time to alarm between
ionization and photoelectric type smoke alarms has been found to be
trivial. In other full-scale fire tests, the difference in response time
has been found to be considerable.
Based upon the above, 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:

It cannot be stated categorically that one type of smoke alarm is better
than any other type of smoke alarm in every fire situation that could
possibly arise in a residence.

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 residence 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.
Additional information on smoke alarms can be found on the USFA, CPSC, and
NIST Web sites.