What Causes a False Alarm in a Smoke Detector?

How Smoke Detectors Work

• Smoke alarms work in two ways. An ionization detector uses an electrical current that detects both invisible and visible smoke particles. A photoelectric detector has a small light beam inside that detects larger, visible smoke particles. Disruption of the electrical current or the light beam causes the alarm to sound. Photoelectric detectors generally have fewer nuisance alarms. Some smoke detectors use both types of technology.

Dust, Dirt and Insects

• Smoke alarms placed in dusty areas like attics or garages often get dirt, dust or insect buildup. The dirt and dust are detected just like smoke particles would be, so the alarms sound. Dirt and dust can also make the alarms extra sensitive, and live insects can trigger alarms as well.

Condensation

• Similar to dust and dirt, steam particles can flood detectors. A smoke detector near an outside door or window may sound a false alarm when condensation gets inside the device. This can happen when a door opens to the colder air outside. Also, don't place smoke detectors too close to bathroom doors where steam from showers escapes.

Smoke

• Smoke detectors are designed to sound alarms when there is smoke, so it makes sense that having them near kitchens can cause false alarms. Smoke from regular cooking or from smoldering plastic in dishwashers easily causes alarms to sound. It's best to install smoke detectors outside of kitchens.

Age

• Old smoke detectors may begin to fail, and false alarms can be a symptom. Detectors should be replaced every eight to 10 years. If you inherited a smoke detector, check the back of the device for the date.

Electrical Disruptions

• If your smoke detector is hard-wired rather than battery-operated, power interruptions or loose wiring can cause the alarm to sound when power is restored. If nuisance alarms happen frequently, check the wiring before replacing the device.