Some Clarifying Points on Smoke Detectors

Smoke detectors have saved thousands of lives. Using them is an essential safety measure for every house.

Types of Detectors

Smoke detectors can have either ionization or photoelectric sensors. Because each type of sensor responds more quickly to a different kind of fire, the best protection is a detector that uses both.

Ionization detectors contain a tiny amount of shielded radioactive material that emits a small amount of radiation that’s detected by a sensor. Smoke blocks the radiation from reaching the sensor, tripping the alarm.

Photoelectric detectors use a small light beam shining on a light-sensitive photocell. An alarm sounds whenever smoke particles interrupt the light beam. The light bulb producing the beam must be replaced about every three years.

An ionization unit responds faster to quick-burning fires with little smoke, such as from paper, wood and fat. They are recommended for work areas and furnace rooms.

A photoelectric model, which is less susceptible to false alarms from normal kitchen fumes, reacts more quickly to slow-burning fires, such as smoldering mattresses and upholstery.

Wired, Plug-In or Battery

In new homes, many local codes require a 120-volt smoke-detection system wired directly into a circuit and installed at the time of construction.

Another type can be plugged into an electrical outlet. With the plug-in type, use an outlet not controlled by a wall switch. Both types have an indicator light that tells you that the detector is receiving power. Either type should have a battery backup in case of power failure.

The widely available battery-operated units are easy to install and give good protection when the batteries are tested regularly. Select a model that beeps when it needs a new battery.

Installation

One smoke detector is not enough for most homes. You should have at least one in each bedroom or adjoining hallway, and one on each floor if your house has more than one story.

Install detectors in the middle of the ceiling, if possible, at least 4 inches away from any wall. Detectors can also be mounted high on walls, 6 to 12 inches from the ceiling.

Avoid areas, such as corners or at ends of hallways, where air--and smoke--do not circulate well. Keep smoke detectors away from drafts at vents, windows and doors.

To install a battery-operated unit, use the screws and anchors that come with it. Position the base bracket on the wall or ceiling and mark the screw locations with a pencil. Drill holes for the anchors and insert them. Then screw the bracket to the anchors. After installing the battery, place the smoke detector over the bracket and snap or twist it into place.

Testing and Cleaning

Test smoke detectors monthly and replace the batteries annually on a specific date, such as Halloween.

Some units can be tested by shining a flashlight on a sensor. On most, you push a button on the detector to test it. If there is no test button, hold a lighted candle 6 inches below the detector. If the alarm doesn’t sound, blow out the candle and let smoke drift into the unit. If it still doesn’t sound, check the battery or circuit.

Dust can reduce a detector’s sensitivity. It’s a good idea about once a month to gently vacuum the detectors using a wand attachment. A detector in a dusty laundry room or workshop especially needs frequent cleaning.

Never disconnect a smoke detector. If nuisance alarms, such as from cooking, are a problem, relocate the detector.