Smoke Alarms


Smoke Alarms Save Lives!

Fire experts consider smoke alarms to be the most effective low-cost warning device available. They are the single most important means of preventing house and apartment fire fatalities by sounding an early warning signal. They are easy to acquire and simple to install and maintain. 

Things to Know About Smoke Alarms

  • When buying smoke alarms look for smoke alarms that bear the label of an independent testing laboratory. DO NOT buy smoke alarms unless they have that label.
  • Smoke alarms can be powered by batteries, plugged in or hard-wired to an electrical system. Know what type is best for your home or business before buying them.
  • Smoke alarms use one of two sensing systems for detecting a fire. They are:
    • Ionization type smoke alarms pass an electric current through a sensing chamber.  When smoke enters the chamber, it interrupts the flow of current and activates the alarm.
    • Photoelectric type smoke alarms aim a light source into a sensing chamber.  Smoke entering the sensing chamber reflects the light onto the photocell and activates the alarm.


Heat and smoke rise, so all alarms should be installed high on a wall or on the ceiling. Install alarms on every level of your home. The National Fire Protection Agency recommends that you sleep with bedroom doors closed to slow the spread of smoke and fumes if there is a fire. Sometimes small children don't wake up to the sound of smoke alarms. Test the alarm outside children's bedrooms while the children are asleep to check their response. If people in your household sleep with doors closed, install interconnected alarms inside sleeping areas as well.

  • Wall-mounted alarms should be installed so that the top of the alarm is 4 to 12 inches from the ceiling.
  • Ceiling-mounted alarms should be placed 4 to 10 inches from any wall. If the ceiling is pitched, mount the unit at or near the highest point.
  • For the best protection, interconnect all smoke alarms. When one smoke alarm sounds they all sound. Interconnection can be done using hard-wiring or wireless technology.

Do not install near a window, door, fireplace or forced-air register where drafts could detour smoke away from the unit.

Position basement alarms close to the bottom of the stairs. Don't place the unit at the top of the stairs; dead air trapped near the closed door could prevent smoke from reaching the unit.


  • Boise Fire recommends purchasing new alarms every 10 years with a 10 year built in battery to avoid the twice per year battery changes.
  • If you have alarms that require batteries to be changed, they should be replaced at least once a year. Pick a certain holiday, birthday or daylight-savings time to help you remember to replace the batteries. Many battery-powered smoke alarms will "chirp" to warn you that their battery power is too low.
  • Clean your smoke alarms twice a year by using a vacuum over and around the alarm to remove dust and cobwebs. Dirty alarms can degrade sensitivity. Never paint any part of a smoke alarm.
  • Test alarms once a month. If your alarm doesn't respond to the manufacturer's recommended test procedure (usually pushing a test button), change its batteries. If it still doesn't perform, replace the alarm. Alarms will last 8 to 10 years. You can write the purchase date with a marker on the inside of your unit, then you will know when to replace it.
  • If you have a problem with nuisance alarms, due to cooking fumes or other non-fire causes, do not disconnect the alarm or remove the batteries. You may not remember to put the batteries back in the alarm after cooking. Instead, wave a towel near the alarm. Try another location or another model of alarm, but keep your home protected. Always be sure you understand why an alarm is sounding before you treat the alarm as a nuisance.

Did You Know?

In 2012-2016, smoke alarms sounded in more than half (53%) of the home fires reported to U.S. fire departments. Almost three of every five home fire deaths resulted from fires in homes with no smoke alarms (40%) or no working smoke alarms (17%). No smoke alarms were present in two out of every five (40%) home fire deaths.

In a house fire, a closed door may slow the spread of smoke, heat and fire. Install smoke alarms in every sleeping room and outside each separate sleeping area. Install alarms on every level of the home. Smoke alarms should be interconnected. When one sounds, they all sound. Press the test button to be sure the alarm is working at least once a month. When a smoke alarm sounds, get outside and stay outside. Replace all smoke alarms in your home every 10 years.

For additional tips and information, read these safety tips and keep your home and family safe from fire.

Safety Tips (PDF)

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