What Do Fire Detectors Have Inside of Them?

Radioactive Materials

• Ionization alarms use small amounts of radioactive materials, americium 241 and radium 246, to ionize the air around the alarm. Ionization is the process of stripping electrons from atoms to create molecules with an electric charge. A small electrical current is sent through the ionized air, and when smoke particles get in the way of the current, the alarm sounds. The radioactive materials in an ionization alarm are contained in a small disc, about 3 to 5 ml in diameter and weighing half a gram. The Environmental Protection Agency says the exposure risk from the materials is low because the radioactive particles can't travel very far, but the International Institute of Concern for Public Health cites a number of health and environmental risks posed by the materials.

Photoelectric Alarms

• Photoelectric alarms use a light source and sensor arranged in such a way that smoke particles that enter the light's path scatter rays onto the sensor, sounding the alarm. Light sources in a photoelectric alarm are either white light or low-power lasers.

Power Sources

• Smoke detectors are either powered by batteries or hard-wired into a home's electrical system. Safety experts recommend checking batteries once a month and changing them out at least once a year. Hard-wired units often use a battery backup system, and those batteries should also be checked frequently and changed at least once per year.

Dust and Debris

• Like most things in your home, smoke alarms need an occasional cleaning. Dust and debris, such as cobwebs, can build up and cause the device to malfunction, sounding false alarms or worse, not sounding when real danger occurs. Gently brush the device once or twice a year for dust and cobwebs. If possible, use a vacuum's hose to remove dust from the inner workings of the smoke detector, to prevent unnecessary contact that could damage the electrical components.