Smoke Alarms and Fires

Fire kills more Americans than all natural disasters combined, and over 80 percent of all fire deaths occur in residences. Direct property loss due to fires in the United States is estimated at $21.9 billion per year. Cooking and smoking are the leading causes of residential fires, followed by heating fixture issues.

Smoke Alarms

A smoke alarm is a battery operated or electrically connected device that senses the presence of visible or invisible particles produced by combustion. When these particles are detected, the device sounds an alarm.

Types of Smoke Alarms

There are two main types of household smoke alarms in common use: ionization and photoelectric smoke alarms. An ionization alarm uses a small amount of radioactive material to ionize air in the sensing chamber. As a result, the air chamber becomes conductive, allowing current to flow between two charged electrodes. When smoke particles enter the chamber, the conductivity of the air in the chamber decreases. When this reduction in conductivity is reduced to a predetermined level, the alarm goes off.

A photoelectric smoke alarm consists of a light emitting diode and a light sensitive sensor in the sensing chamber. The presence of suspended smoke particles in the chamber scatters the light beam. This scattered light is detected, and the alarm is set off. While photoelectric smoke alarms are certainly used, ionization alarms are more common.

Maintenance of Smoke Alarms

Smoke alarms should be maintained in accordance with the manufacturers' instructions. Lightly vacuuming the alarm occasionally will keep the alarms air vents clean and will help the device work properly. Due to the normal low battery drain of ionization smoke alarms, long-life smoke alarms have been designed to use lithium batteries and can last up to ten years.

Although the batteries smoke alarms use may be designed to last 10 years, ongoing testing and maintenance is required to make sure these important devices continue to work properly. Smoke alarms should be replaced every 10 years and checked monthly, and are designed to provide an audible signal when the alarm's battery gets low.