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Home Smoke Alarms


Smoke alarms do save lives, but only if they are properly installed and functioning.  Most fatalities happen in homes without working smoke alarms. Your fire department recommends that you have smoke alarms installed in every sleeping room, outside each separate sleeping area and on every level of the home, including the basement.  If you have more questions about smoke alarms be sure to contact the fire department at 425 430-7000.


  • Smoke alarms should be installed in every sleeping room, outside each separate sleeping area and on every level of the home, including basements.
  • Larger homes may require additional smoke alarms to provide a minimum level of protection.
  • Mount smoke alarms high on a wall or on the ceiling following the manufacturers instructions.
  • In a room with a pitched ceiling, place the alarm at or near the ceiling's highest point.
  • Basement alarms should be located close to the stairway leading to the floor above.
  • Ceiling mounted alarms should be placed a minimum of four (4) inches from the nearest wall.
  • Wall mounted alarms should be four (4) to eight (8) inches from the ceiling.
  • Do not install alarms within three (3) feet of a kitchen or bathroom opening.


  • Follow the manufacturer's instructions.
  • Have a qualified electrician install hard-wired alarms.
  • Never connect an alarm to a circuit that can be shut off with a switch.
  • Interconnect all smoke alarms through the home, when one sounds they all sound.
  • Wireless battery-operated interconnected smoke alarms are now available.
  • An ionization smoke alarm is generally more responsive to flaming type fires.
  • A photoelectric smoke alarm is generally more responsive to smoldering fires.
  • When extra time is needed to awaken or assist others, both types of alarms are recommended.
  • Choose smoke alarms that have the label of a recognized testing laboratory.

Testing and Maintenance

  • Test smoke alarms at least once a month using the test button.
  • Make sure everyone in the home understand the warning of the smoke alarm and how to respond.
  • Dust or vacuum smoke alarms annually and/or whenever the battery is changed.  Follow manufacturer's instructions for cleaning.
  • Smoke alarms with non-replaceable (long-life) batteries are designed to remain effective for up to 10 years.
  • If a long-life battery operated smoke alarm chirps, warning the battery is low, replace the entire smoke alarm right away.
  • For smoke alarms with any other type of battery, replace batteries at least once a year, if the alarm chirps, replace the battery.
  • Replace smoke alarms if they are more than ten years old or sooner if they do not respond properly when tested.
  • All rental units need working smoke alarms.
  • If you rent and don not have working smoke alarms, contact your landlord or property manager immediately to have them installed.
  • NEVER "borrow" a battery from a smoke alarm.
  • Never disconnect the battery to silence the alarm.  If an alarm sounds because of cooking wave a towel or other item, introduce fresh air, and stop the alarm. 
  • Some alarms come with a hush feature that will allow you to silence a false alarm.

Ionization and Photoelectric... What is the difference?

There are two types of smoke alarms designed for homes. One type is called an ionization alarm because it uses "ions," or electrically charged particles, to detect smoke in the air. Smoke particles entering the sensing chamber change the electrical balance of the air. The greater the amount of smoke, the higher the electrical imbalance. The horn will sound when the electrical imbalance reaches a preset level.

The other type of alarm is called photoelectric because its sensing chamber uses a beam of light and a light sensor. The sensing chamber is designed so that the light beam does not strike the sensor, but smoke particles entering the chamber deflect the light onto the sensor. The greater the amount of smoke entering the chamber, the more light will be deflected onto the sensor. The alarm sounds when the amount of light hitting the sensor reaches a preset level.

Both types can meet the test standards of Underwriters Laboratories, but each has its own advantages. The ionization alarm responds faster to small smoke particles, while the photoelectric responds faster to large smoke particles. Flaming fires produce more small smoke particles and smoldering fires produce more large particles.

An important fact to know is that ten-year batteries will not last for their stated service life in photoelectric smoke alarms because this type of smoke alarm uses more power than an ionization type. However, there is nothing wrong with installing a long-life battery in them as long as you remember to replace the smoke alarm itself when it is ten years old.