The 411 on Smoke Alarms: What You Need to Know

Testing and replacing smoke detectors is kind of like eating right: Everyone knows they should do it, but who really has the time?

Well, the Federal Emergency Management Agency (FEMA) and lots of other government agencies suggest you make the time.

After all, FEMA points out that properly installed and maintained smoke alarms are the only thing that can alert you and your family to a fire 24 hours a day, seven days a week. According to the National Fire Protection Association, almost two-thirds of home fire deaths resulted from fires in properties without working smoke detectors.

Beth Anne Nesselt in the Montgomery County Fire and Rescue Public Information Office agreed. “Smoke detectors save lives and should be in every home,” she said.

Many area homes are either approaching or have reached the age at which their smoke detectors need replacing. So where to start? First, buy the right kind of smoke detector. There are two main types: ionization and photoelectric.

According to the National Fire Protection Association, ionization-type smoke detectors feature two electrically charged plates with a small amount of radioactive material between them, which ionizes the air and causes current to flow between the plates. Smoke disrupts the flow of ions and activates the alarm.

By contrast, photoelectric-type detectors aim a light source into a chamber. When smoke enters, it reflects the light onto a sensor and triggers the alarm.

Because the two types operate differently and are better at detecting different kinds of fires, Nesselt suggested you either install both types in your home or buy detectors that feature both ionization and photoelectric smoke sensors.

In addition, if you or a family member has a hearing disability, buy a detector that also has a strobe light.

Most newer, large homes have smoke detectors that are hard-wired to the electrical system so that if one goes off on a lower floor, all of them will sound and people upstairs will hear them. However, each detector should also have a battery backup in case the power goes out, and batteries should be replaced regularly.

Nesselt also strongly advised having smoke detectors on all levels of the home, including the basement. Because many fatal fires begin late at night or early in the morning, install them both inside and outside of sleeping areas. Always follow the manufacturer’s installation instructions to the letter, or hire an experienced contractor to install your smoke detectors.

The Montgomery County Fire and Rescue Service will assist with installation of battery-operated smoke detectors only at no charge. Call the Home Fire Safety Evaluation Hotline at 311 to schedule an appointment.

Even a properly installed smoke detector is useless without proper maintenance, of course. Again, follow the manufacturer’s instructions, but be mindful of these general FEMA guidelines:

Smoke detector powered by a 9-volt battery:

  • Test the alarm monthly.
  • Replace the batteries at least once per year.
  • Replace the entire smoke detector unit every 8 – 10 years.

Smoke detector powered by a 10-year lithium (or “long life”) battery:

  • Test the alarm monthly.
  • Since you cannot (and should not) replace the lithium battery, replace the entire smoke detector unit according to manufacturer’s instructions.

Smoke detector that is hard-wired into the home’s electrical system:

  • Test the alarm monthly.
  • Replace the backup battery at least once per year.
  • Replace the entire smoke detector unit every 8 – 10 years.

“Remember that smoke detectors aren’t lifetime appliances,” Nesselt cautioned.

She added that as a smoke detector ages, it becomes more sensitive and prone to false alarms. That’s your cue to replace it and help keep your family safe.