Editor’s note: This story was originally published in October 2021.
Few things are more jarring than waking up in the middle of the night to the blaring alarm of a smoke detector — particularly if there is no fire to be found.
Smoke detectors can be triggered for a variety of reasons unrelated to house fires, from dust and cobwebs to simply old batteries. Simple cleaning and maintenance can prevent future rude awakenings.
Joe Thomas, Maine State Fire Marshal, said that he likes to think about these unexpected smokeless triggers as “nuisance alarms.”
Smoke detectors are generally triggered by particulates floating through their sensors. The burnt bits that make up smoke are one such particulate, but they aren’t the only matter that can float around the air of your house.
“People call it a false alarm, but in some cases it’s not false — it’s doing exactly what it’s supposed to do,” Thomas said.
The first step to figuring out what might be causing a smoke detector to go off is to determine whether it is producing an actual alarm or a “chirp.”
“If it’s continuously chirping as opposed to giving a real alarm sound, that indicates that the battery needs to be replaced,” Thomas said.
If you have already checked the batteries and the device is still wailing, though, the likely culprit is a dirty smoke detector.
“The internal device that reacts to the smoke particles, it can’t tell the difference between the smoke particle and the dust particle,” Thomas said. “If you have a cobweb up there and you have a spider up there the spider walking through can have the same effect.”
Turning on the heat — which many Mainers are doing at this time of year — can trigger a smoke alarm for a similar reason.
“You now have a different air flow than you did before,” Thomas said. “It could be the build up of dust on the radiator that should have been vacuumed off before you turned it on.”
Thomas said to make sure you are cleaning your smoke detector with a vacuum cleaner two to three times a year.
“Good maintenance by vacuuming the sensors periodically is a good thing to do. These maintenance issues aren’t going to be dealt with at 3 o’clock in the morning. It’s more important that people think about these throughout the year and have good maintenance.”
In a home that has a lot of dust from burning wood or that has the windows open a lot of the time, sensors should be regularly cleaned and then tested, according to Todd Smith, operations manager at Maine Fire Equipment Co.
“There is a canned smoke we sell used for testing the sensor or a perfectly burned piece of toast will usually do the trick as well,” Smith said.
Location also matters. Certain smoke detectors can also be triggered by humidity, including steam from hot showers. Exposure to cold can also impact battery life of smoke detectors.
“I have detectors in my garage and my battery backup does not last as long as detectors in the house because cold affects them,” Thomas said.
The cause of nuisance alarms could be more technical, too. Thomas said to check for loose connections in hardwired detectors. Power interruptions during the night could cause smoke detectors to go off.
“It may be going through the battery and the battery may be faulty and it’s causing some kind of reaction to it,” Thomas said.
If you clean it and check for maintenance issues and it still goes off, though, Thomas said it might be time to replace it.
“That being said you can also have a faulty smoke detector,” Thomas said. “If it continuously keeps going off, the best thing to do is simply replace it.”
