Why Does My Smoke Detector Go off When I Shower?

Function

• Smoke detectors function in one of two ways with a photoelectric eye or a compartment containing a minute amount of radioactive material to sense smoke. The smoke either interrupts the light beam in a photoelectric detector or interrupts the electrical current in ionization models.

Humidity

• Thick humidity can mimic smoke and set off a detector. Hot showers generate humidity clouds, which can trigger smoke alarms mounted in close proximity to bathrooms. The thick air enters the detection chamber and interrupts the light beam or current just as smoke would do. The detector cannot tell the difference between smoke and humidity, so its alarm sounds. Condensation inside the unit from humidity exposure can also set the alarm off, according to the Wake County Fire Marshall's Office.

Prevention

• Do not mount smoke detectors near bathrooms to prevent humidity-related false alarms. Place the units in areas where fires are most likely to start. For example, dropped cigarettes could catch furniture on fire in living areas, and photoelectric models are good at detecting smoldering fires, so mount them in living rooms and family rooms. Ionization units react quickly to blazing fires, so put them in kitchens, which have ignition sources like stoves and other appliances, and in utility rooms where you store flammables. Humidity should not pose a problem in any of those rooms.

Considerations

• Smoke detectors that were not triggered by showering for many years might suddenly start going off from the humidity. These false alarms happen because some models get more sensitive as they age. Replace the smoke detector if it is older and starts reacting to showers. Replace any alarms in your home that are over 10 years old, even if they seem to function correctly, because smoke detectors have a limited lifespan.

Warning

• Never take the battery out of a smoke detector mounted near a bathroom if it keeps going off with false alarms when you shower. Move the detector to a more appropriate area. You render the unit useless without a battery, leaving you unprotected if a fire breaks out.