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Although they are small and in expensive, smoke detectors can play a priceless protective role. If properly located, they will sound an alarm early enough to enable you to escape from a fire.
Different Sensing Methods: Smoke detectors come in two forms: In a chamber of the ionization type of detector, electrically charged particles flood a gap between two terminals. Normally the particles carry current, but smoke from a fire disrupts the flow and triggers the alarm. In a photoelectric detector, the alarm is tripped when smoke deflects a beam of light onto a light-sensitive switch.
Ionization detectors respond quickly to smoke from clean-burning fires of paper and wood. However, they tend to sound false alarms when exposed to ordinary household fumes and kitchen smoke.
Photoelectric detectors respond slowly to clean-burning fires but quickly to the slow-burning, smoldering fires that occur most frequently in houses—those that produce heavy smoke and are most likely to start in a kitchen, base- merit, bedroom, or living room.
Battery Backup: Although some detectors operate on the house’s electrical current, many models are battery powered and can be installed without difficulty wherever you need them. They also continue to provide protection in the event of a power failure— a likely occurrence in an electrical fire. If your house has hard- wired detectors that lack battery backup, install battery-powered ones next to them.
Most detectors sound a beep when the battery runs low. Even if no low-battery indicator sounds, change the batteries once a year. (An easy-to-remember system is to replace them every autumn when you set back the clock from daylight-saving time.) If you move into a new house or apartment, replace all the batteries at once.
86 Locating detectors in a house. Since most fatal fires occur at night, install detectors in hallways outside bedrooms. Some smoke detectors also contain heat sensors, which are useful in furnace rooms, where a rapid rise in temperature can occur before fire breaks out. Install at least one detector on every floor. Set one at the head of a stairwell. Place additional detectors in rooms where fires commonly start; in a kitchen, use a photoelectric model, which will not react to normal cooking fumes. Install extra detectors ac cording to a household’s particular circum stances—for example, directly over a sleeping area if that person smokes in bed.
Some communities strictly regulate the placement of smoke detectors. Check with local fire authorities for any special requirements.
In most rooms, install a ceiling-mounted detector at least 4 inches from a wall; place a wall-mounted unit no less than 4 inches from the ceiling. In rooms with cathedral or A-frame ceilings, position the smoke detector about 12 inches below the peak of the ceiling. On a beamed ceiling, install the detector on the bottom of a beam, not in the space between beams.
An occasional cleaning prevents dust buildups that can cause a detector to malfunction or to sound false alarms. The upholstery nozzle of a vacuum cleaner is ideal for removing dust or cobwebs. An air blower such as the one at right, available at camera stores, blows dust out of crevices.