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Smoke Detectors Work

A universtiy 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 Type 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. Photo-electric detectors - These type 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 you want to protect, where fire would be most dangerous, how many you will need,
etc.

It is recommended that every home have a smoke detector outside each sleeping area (inside as
well if members of the household sleep with the door closed) and on every level of the home,
including the basement. 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.

Installation

The placement of smoke detectors is very important and always follow the manufacturer's
directions. Sleeping areas need the most protection. 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 you should put a smoke detector in your kitchen, be sure to keep it
away from cooking flames or smoking areas.

Proper mounting of a smoke detector also is important. You can mount many detectors by
yourself but those connected to your household wiring should have their own separate circuit and
be installed by a professional electrician. If you mount your detector 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 year 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.

Check the smoke detector every 30 days by releasing smoke or pushing the test button. Clean the
detector face and grillwork often to remove dust and grease. Never paint a smoke detector as it
will hamper its function. Check your detector if you've been away from home.