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Smoke Detectors
Smoke detectors are devices that are mounted on the wall or ceiling
and automatically sound a warning when they sense smoke or other
products of combustion.
Although everyone likes to feel safe at home, about two-thirds
of our nation's fire deaths happen in the victim's own home. The
home is where their is the greatest risk and where residentstake
the most precautions. Most deaths occur from inhaling smoke or poisonous
gases, not from the flames.
Most fatal fires occur in residential buildings between 11 p.m.
and 6 a.m. when occupants are more likely to be asleep. More than
90 percent of fire deaths in buildings occur in residential dwellings.
A John Hopkins University study, funded by the United States Fire
Administration, found that 75 percent of residential fire deaths
and 84 percent of residential fire injuries could have been prevented
by smoke detectors.
There are two basic types of smoke detectors:
1. Ionization detectors - Ionization detectors contain radioactive
material that ionizes the air, making an electrical path. When smoke
enters, the smoke molecules attach themselves to the ions. The change
in electric current flow triggers the alarm. The radioactive material
is called americium. It's a radioactive metallic element produced
by bombardment of plutonium with high-energy neutrons. The amount
is very small and not harmful.
2. Photoelectric detectors - these types of detectors contain
a light source (usually a bulb) and a photocell, which is activated
by light. Light from the bulb reflects off the smoke particles and
is directed towards the photocell. The photocell then is activated
to trigger the alarm.
Choosing a smoke detector
When choosing a smoke detector, there are several things to consider.
Think about which areas of the house that need protection. Where
would fire be most dangerous? How many detectors are needed?
The Chula Vista Fire Department recommends that every home have
a smoke detector in the hallway, and each bedroom of a home. On
floors without bedrooms, detectors should be installed in or near
living areas, such as dens, living rooms or family rooms. Smoke
detectors are not recommended for kitchens.
The safest bet is to have both kinds or a combination detector
with a battery back up. Be sure to check for a testing laboratory
label on the detector. It means that samples of that particular
model have been tested under operating conditions. Check to see
if it is easy to maintain and clean. Make sure the batteries are
common and easy to replace.
Installation
The placement of smoke detectors is very important. Sleeping areas
need the most protection. A smoke detector should be located in
each bedroom of the home. One detector in a short hallway outside
the bedroom area is usually adequate. Hallways longer than 30 feet
should have one at each end. For maximum protection, install a detector
in each bedroom.
Be sure to keep the detector away from fireplaces and wood stoves
to avoid false alarms. Place smoke detectors at the top of each
stairwell and at the end of each long hallway. Smoke rises easily
through stairwells. If a smoke detector is installed in the kitchen,
be sure to keep it away from cooking fumes or smoking areas.
Proper mounting of a smoke detector also is important. Many detectors
can be mounted by the resident, but those connected to your household
wiring should have their own separate circuit and be installed by
a professional electrician. If a detector is mounted on the ceiling,
be sure to keep it at least 18 inches away from dead air space near
walls and corners. If you mount it on the wall, place it six to
12 inches below the ceiling and away from corners. Keep them high
because smoke rises.
Never place them any closer than three feet from an air register
that might recirculate smoke. Don't place them near doorways or
windows where drafts could impair the detector operation. Don't
place them on an uninsulated exterior wall or ceiling. Temperature
extremes can affect the batteries.
Maintenance
Keeping smoke detectors in good condition is easy. Always follow
the manufacturer's instructions. Be sure to replace the batteries
every six months or as needed. Most models will make a chirping,
popping or beeping sound when the battery is losing its charge.
When this sound is heard, install a fresh battery, preferably an
alkaline type.
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