Smoke Detectors

The majority of fatal home fires happen at night when people are asleep. Contrary to popular belief, the smell of smoke may not wake a sleeping person. The poisonous gases and smoke produced by a fire can numb the senses and put you into a deeper sleep.

Inexpensive household smoke detectors sound an alarm, alerting you to a fire. By giving you time to escape, smoke detectors cut your risk of dying in a home fire nearly in half. Smoke detectors save so many lives that most states and provinces have laws requiring them in private homes.

Choosing a Detector

Be sure that the smoke detectors you buy carry the label of an independent testing laboratory, such as Underwriters Laboratories of Canada (ULC). Some run on batteries, others on household current. Some detect smoke using an “ionization” sensor, others use a “photoelectric” detection system. All approved smoke detectors, regardless of type, will offer adequate protection provided they are installed and maintained properly.

The Ionization Alarm contains a radioactive source in a smoke chamber that emits radiation, resulting in a weak flow of electric current. When particles such as those produced by fire enter the smoke chamber, they produce the current and trigger the alarm.

The Photoelectric Alarm contains a light source and a special photosensitive cell in a darkened chamber. The cell and light are positioned within the alarm so that either the light beam is interrupted by the smoke as in the obscuration type or the beam is deflected into the cell as in the light scattering type.

Which is better, the ionization or the photoelectric type? Both types of alarms are equally effective in the home. If properly installed, they can provide adequate warning for the family. Some differences exist between the two when they operate close to the origin of the fire. These differences, however, are not critical.

What Kind of Smoke Alarm Do I have?

Ionization smoke alarms work best at detecting fires with flames.

Look on the back of the detector. It will say Ionization, or will have an I symbol, or will have a Radioactive symbol (), or will have a Red Triangle symbol ().

Photoelectric smoke alarms are most effective at detecting smoldering, smokey fires. Look on the back of the detector. It will say Photoelectric, or will say Dual Sensor, or will have a P symbol, or will have a Blue Triangle symbol ().

The national agency that tests smoke alarms recommends having both types of technology in your home.

Is One Enough?

Every home should have a smoke detector outside each sleeping area and on every level of the home, including the basement. The National Fire Alarm Code, developed by NFPA, requires a smoke detector in each sleeping room for new construction. On floors without bedrooms, detectors should be installed in or near living areas, such as dens, living rooms, or family rooms.

Be sure everyone sleeping in your home can hear your smoke detectors’ alarms. If any residents are hearing-impaired or sleep with bedroom doors closed, install additional detectors inside sleeping areas as well. There are special smoke detectors for the hearing-impaired; these flash a light in addition to sounding an audible alarm.

For extra protection, NFPA suggests installing detectors in dining rooms, furnace rooms, utility rooms, land hallways. Smoke detectors are not recommended for kitchens, bathrooms, or garages—where cooking fumes, steam, or exhaust fumes could set off false alarms–or for attics and other unheated spaces where humidity and temperature changes might affect a detector’s operation.

Where to Install

Because smoke rises, mount detectors high on a wall or on the ceiling. Wall-mounted units should be mounted so that the top of the detector is 4 to 12 inches (10 to 30 centimeters) from the ceiling. A ceiling- mounted detector should be attached at least 4 inches (10 centimeters) from the nearest wall. In a room with a pitched ceiling, mount the detector at or near the ceiling’s highest point.

In stairways with no doors at the top or bottom, position smoke detectors anywhere in the path of smoke moving up the stairs. But always position smoke detectors at the bottom of closed stairways, such as those leading from the basement, because dead air trapped near the door at the top of a stairway could prevent smoke from reaching a detector located at the top. Don’t install a smoke detector too near a window, door, or forced -air register where drafts could interfere with the detectors operation.


Most battery-powered smoke detectors and detectors that plug into wall outlets can be installed using only a drill and a screwdriver, by following the manufacturer’s instructions. Plug-in detectors must have the restraining devices so they cannot be unplugged by accident. Detectors can also be hard-wired into a building’s electrical system. Hard-wired detectors should be installed by a qualified electrician. Never connect a smoke detector to a circuit that can be turned off from a wall switch.

False Alarms

Cooking vapors and steam sometimes set off a smoke detector. To correct this, try moving the detector away from the kitchen or bathroom, or install an exhaust fan. Cleaning your detector regularly, according to manufacture’s instructions, may also help. If nuisance alarms persist, do not disable the detector, replace it.


  • Follow manufacturer’s instructions, test all your smoke detectors monthly and install new batteries at least once a year.
  • Replace batteries when you set the clocks back in the fall, for example, or when a detector is “chirping” to indicate that the battery is low.
  • Clean your smoke detector using a vacuum cleaner without removing the detector’s cover.
  • Never paint a smoke detector.
  • Smoke detectors don’t last forever. Replace any smoke detector that is more than 10 years old.

Plan and Practice

  • Make sure everyone is familiar with the sound of the detectors alarm.
  • Plan escape routes. Once a fire has started, it spreads rapidly. You may have only seconds to get out. Know at least two ways out of each room. Second story windows may need an escape ladder to enable occupants to escape safely.
  • Agree on a meeting place outside your home where all the residents will gather after they escape.
  • Practice your escape plan at least twice a year.
  • Remove obstructions from doors and windows needed for escape.
  • Make sure everyone in the household can unlock doors and windows quickly, even in the dark.
  • Windows or doors with security bars should be equipped with quick-release devices and everyone in the household should know how to use them.
  • When the alarm sounds, leave immediately. Do not waste time getting dressed or gathering valuables. Go directly to your meeting place and call the fire department from a neighbor’s phone.
  • Once you’re out, stay out…….never return to a burning building.


  • Careless use of smoking materials is the greatest single cause of deaths by fire.
  • Over 40% of accidental fire victims are asleep at the time of fire.
  • 85% of fire fatalities occur in residential fires.