Ohio State University Extension
Home fires are a serious threat to your family's safety. Every
year in the United States, approximately 5,000 people are
killed and more than 40,000 are injured by residential fires.
In addition, more than $8 billion worth of property damage
is done by home fires. Many fire victims die of inhalation
of smoke and toxic gases, not because of burns. Most deaths
and injuries occur in fires that happen at night while the
victims are asleep. Sleepers must be warned before it is too
late.
When
properly installed and maintained, the home smoke detector
is one of the best and least expensive ways to provide early
warning when a fire begins. Before the concentration of smoke
reaches a dangerous level, or before the fire becomes too
intense, the alarm will sound. Smoke detectors save lives,
prevent injuries and minimize property damage. The risk of
dying from fire is twice as high in homes that do not have
functioning detectors.
Smoke detectors work by sensing the rising smoke from a fire
and sounding a piercing alarm. There are two types of smoke
detectors on the market today:
Ionization
Chamber detectors use a radioactive source to produce
electrically charged molecules (ions) in the air. This sets
up an electric current within the detector chamber. When smoke
enters the chamber, it attaches itself to the ions and reduces
the flow of electric current, thus setting off an alarm.
Photoelectric
detectors sound when the smoke is dense enough to deflect
a beam of light.
Smoke
detectors also differ by power source. The batteries in battery-powered
smoke detectors last approximately one year. When the battery
begins to lose power and needs to be replaced, the detector
will begin to emit "beeps" every minute or so. Some will keep
this up for a week or longer.
Smoke
detectors that operate on household electric current operate
as long as there is current in the circuit to which they are
connected. They are, therefore, vulnerable to power failure.
Plug-in units must be located near an electric outlet where
they will not be unplugged or turned off by a wall switch.
They should not get their power from a distant plug using
an extension cord. Always use the hold-in clips to prevent
accidental plug removal from the outlet.
Heat
detectors are also available, sometimes a part of a smoke
detector and sometimes as separate products. These use a special
metal that melts or distorts when heat enters the air surrounding
it. When built into smoke detectors, these set off the smoke
detectors main alarm. Alone, they may sound their own alarm
or a central alarm, if part of a system. Heat detectors add
protection, but by themselves are not effective early-warning
devices. They must be very close to a fire to be set off.
Therefore, they are useful in places where smoke detectors
can be fooled, such as a kitchen. They are also useful in
areas of the home where smoke detectors cannot function because
it is too hot or cold. Remember, smoke, not heat, is the leading
cause of death in home fires.
Each type of detector, if properly installed and maintained,
is effective. Since photoelectric detectors react more quickly
to smoldering fires and ionization units will respond faster
to flaming fires, you may wish to buy at least one unit of each
or a combination detector. However, because most home fires
produce a mixture of smoke types with detectable amounts of
large particle and small particle smoke early in the fire growth,
either an ionization or a photoelectric detector will meet most
needs.
Several
new features are available in smoke detectors today. These
include detectors that have an escape light, are portable,
or transmit their alarm to a central console by radio signal
as part of a unified emergency alert system. These can be
used with burglar and other warning or detection devices.
Electric current detectors with a rechargeable battery for
power outages are also available.
There should be at least one smoke detector on every floor of
the house. Tests conducted by the National Bureau of Standards
have shown that two detectors, on different levels of a two-story
home, are twice as likely to provide enough time for escape
as one detector. Although the upstairs detector senses smoke
wherever it originates, the downstairs unit will react sooner
to a fire that could block escape routes on the first floor.
Having
two detectors also allows you to select both an ionization
type and a photoelectric model, giving you the best capabilities
of both. In addition, it lets you select one battery-powered
and one plug-in or wired-in model. Neither a battery failure
nor a power outage will leave your family unprotected. Finally,
two smoke detectors are far less likely to be inoperative
at the same time as is possible with a lone detector.
- U.S.
Consumer Product Safety Commission, What You Should Know
About Smoke Detectors (January 1985).
- Acknowledgments
to Michelle L. Wallingford for her contributions to this
publication
Disclaimer
and Reproduction Information: Information in NASD does not
represent NIOSH policy. Information included in NASD appears
by permission of the author and/or copyright holder. More
NASD Review: 04/2002
This document was published as
AEX-690.1
,
Ohio State University Extension, Columbus, Ohio 43210. Funded
in whole or in part from Grant Number U05/CCU506070-02, "Cooperative
Agreement Program for Agricultural Health Promotion Systems,"
National Institute for Occupational Safety and Health. Publication
Date: June 1992.
Ohio
State University Extension, Columbus, Ohio 43210. Reviewed
by Mr. Randall Reeder and Dr. Jim Papritan, Department of
Agricultural Engineering, and Dr. Judy Wessel, Department
of Family Resource Management.
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