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Guidelines for Smoke Alarms

Working smoke alarms save lives. Don’t be foolish enough to think a barking dog will awaken you or that you will smell smoke – don’t bet your life on it!

Smoke Kills

Toxic smoke and fumes kill. In a house fire, it is the flames that do the structural damage, but smoke is the primary danger to people. The majority of deaths in fires come from smoke poisoning.

Modern homes contain many materials, such as wood, wool, nylon and plastics, which when burning, produce heavy smoke and toxic fumes such as carbon monoxide and cyanide gas. These materials can smoulder for extended periods of time, producing substantial smoke and fumes before they burst into visible flames.

If you are asleep when a fire starts, you could suffer from smoke inhalation before you wake up. In fact, the combination of toxic smoke and gases and reduced levels of oxygen in the air can make waking up extremely difficult and in some circumstances, tragically impossible. So, it is essential to install and maintain working smoke alarms that will detect the smoke and sound an alarm.

Recent research indicates that house fires today burn faster and kill quicker than house fires 30 years ago. Research in the 1970s showed a safe escape time of 17 minutes. In 2005, this has decreased to an escape time of 3 minutes, or less in some circumstances. This drastic drop in escape time is primarily due to the contents of our modern homes, such as furnishings, that burn faster and more intently. This reduced escape time highlights the need for home fire escape planning and performing periodic practice drills.

Smoke Alarm Facts

  • Over 90% of residential fires in Ontario are preventable.
  • An injury is reported in 1 out of every 17 preventable home fires, and not all injuries are reported.
  • 1 out of every 100 preventable residential fires is a fatal fire.

Research from 1995 to 2004 regarding preventable, fatal residential fires in Ontario indicates:

  • 35% of fires – a smoke alarm was present and operated.
  • 25% of fires – a smoke alarm was present and did not operate.
  • 21% of fires – no smoke alarm was present.
  • 19% of fires – smoke alarm operation was undetermined.

This research pertains to 609 fatal fires that occurred in Ontario from 1995 to 2004. In about 50 per cent of fatal home fires, there was no smoke alarm warning. In the majority of these fatal home fires, it was determined a dead battery or no battery installed was the reason for the smoke alarm failing to activate.

Statistics also indicate the holiday season between November and the end of January to be the highest point of the year for fires and related fatalities. From November 1, 2004 to January 31, 2005, alone there were 35 fire fatalities in Ontario. This highlights the need to exercise extra caution during the holiday season when we may be most distracted.

(Statistical Source: Office of the Ontario Fire Marshal)

Smoke Alarms vs. Smoke Detectors

Often you hear people using the terms smoke alarms and smoke detectors interchangeably. However, there is a difference between the two. What’s the difference?

A smoke alarm is an all-in-one, self-contained device, with a detector, which senses the products of combustion (smoke) and sounds an audible, and sometimes visual warning or alarm. Smoke alarms are widely used in residential settings. Put simply, a smoke alarm detects smoke and sounds an alarm.

A smoke detector is strictly a sensing device only, which senses the products of combustion (smoke) and sends a signal to a building’s fire alarm system to activate an audible, and sometimes visual warning or alarm. Smoke detectors must be connected to a building’s fire alarm system and are NOT a stand-alone unit. Put simply, a smoke detector senses smoke only and must be connected to a fire alarm system control panel. Smoke detectors are a detection device only – not an alarm.

Smoke Alarm Technologies and Features


There are two types of technologies used in smoke alarms to detect the presence of smoke or the products of combustion. Smoke alarms will employ one or both of these types of technologies. Each type of detector has its advantages and disadvantages.

Ionization smoke alarms activate more quickly for fast, flaming fires with little visible smoke. Photoelectric smoke alarms are particularly more responsive to smouldering fires and the dense smoke given off by foam-filled furnishings.

When properly installed and maintained, both types of alarms alert you to a fire and save lives. As in all things relating to your family’s safety, buy the highest quality smoke alarm your budget will allow. Do not select a detector based solely on its low cost.

Smoke alarms are designed to be battery-powered or powered by a permanent connection to the household alternating current (AC) electrical supply (110v).
It is important when replacing smoke alarms that the correct type is installed. Smoke alarms that are installed with permanent electrical connections, also known as direct-wired or hard-wired smoke alarms, cannot be replaced with battery-powered units.

When purchasing a smoke alarm, look for a product that has been manufactured and tested to an acceptable standard, indicated by a marking for the Underwriters Laboratories of Canada (ULC), or Underwriters Laboratories Incorporated (cUL).

smoke alarm UL Logo

Ionization Smoke Alarms

Ionization smoke alarms use a small amount of radioactive material that ionizes the air between two electrically charged plates, causing a current to flow between the plates. When smoke enters the chamber, it changes the flow of current, which is detected and activates the alarm.

Ionization smoke alarms activate more quickly for fast, flaming fires with little visible smoke.


  • Cheaper than other types of smoke alarms
  • Very good with fast flaming fires with little visible smoke
  • Suitable for general use
  • Less prone to false alarms due to dust and steam


  • Very susceptible to nuisance alarms due to cooking
  • May be slow to respond to slow smouldering fires
  • Contain radioactive material

Photoelectric (Optical) Smoke Alarms

A photoelectric (optical) smoke alarm “sees” the smoke. NOTE: The term photoelectric does not refer to the power source for the smoke alarm. The power supply can be battery or direct-wired on the household electrical current (110v A/C). Both types are available to the consumer. Photoelectric (optical) smoke alarms operate on the principle of light scattered from the surface of particles. Smoke entering the sensing chamber reflects light onto the sensor, which triggers the alarm. Because large particles have much more surface area than small particles, a photoelectric smoke alarm is more sensitive to the large smoke particles produced in a smouldering fire.Photoelectric (optical) smoke alarms are particularly more responsive to smouldering fires and the dense smoke given off by foam-filled furnishings.

Smoke Alarm Photoelectric type


  • Good for smouldering fires and dense smoke
  • Not as prone to cooking nuisance alarms
  • Contain no radioactive material
  • Suitable for general use


  • Prone to nuisance alarms from dust and insects – must be kept clean
  • More expensive

In the normal case, the light from the light source shoots straight across and misses the sensor. When smoke enters the chamber, however, the smoke particles scatter the light and some amount of light hits the sensor, activating the alarm.

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Combination Ionization / Photoelectric (Optical) Smoke Alarms

Combination Ionization / Photoelectric (Optical) alarms combine the two technologies, ionization and photoelectric, to detect the presence of smoke or products of combustion. An alarm can be activated by either of the sensors within the unit. A combination Ionization / Photoelectric (Optical) alarm gives you the benefits of both types of technologies.

Combination Smoke Alarm / Carbon Monoxide Alarm

Smoke alarms that combine carbon monoxide detection and smoke detection capabilities are also available in a single unit. These units incorporate different sounding alarms, or in some cases voice alerting of “Fire / Fire” or “Warning Carbon Monoxide” when detecting the presence of smoke and/or carbon monoxide. If a combination smoke alarm / carbon monoxide alarm is used, it must be installed on the ceiling to ensure that it will detect smoke effectively. Follow the manufacturers instructions.

Battery-Operated Smoke Alarms and Direct-Wired or Hard-Wired (A/C) Smoke Alarms

A 9v alkaline battery powers most battery-operated smoke alarms. Some manufacturers also offer battery-operated smoke alarms powered by a long-life lithium battery.

The Ontario Building Code has required direct-wired smoke alarms be installed in all new home construction since 1986, with amendments and additional requirements over the years.

When smoke alarms are being replaced, the replacement unit must not reduce the level of detection required by the Building Code in effect at the time of construction of the residence, or by municipal by-laws in effect before the Fire Code adopted this requirement. This requirement is contained in Sentence the Fire Code. In other words, existing direct-wired or hard-wired smoke alarms or electrically interconnected smoke alarm installations must be maintained to provide the same level of protection as originally required. Any replacement smoke alarms must be of a type comparable to the original or better. Any smoke alarms installed in addition to the requirements of Section 2.13 of the Fire Code are permitted to be battery powered.

Direct-wired smoke alarms can be “interconnected” or linked to one another, which means that should one smoke alarm activate in the home it will automatically sound the alarm on all smoke alarms within the home that are connected. People who sleep with their bedroom doors closed or may have difficulty awakening to a smoke alarm sounding outside the sleeping area should strongly consider installing interconnected direct-wired smoke alarms in their home.

Remember, smoke alarms connected directly to your home’s electrical power supply (A/C) will not work during hydro outages unless they have a battery back up feature. Some older models of these alarms do not have an internal battery backup. Find out what type of alarms you have in your home and ensure you are protected by battery operated smoke alarms in the event of a power failure in your home.

Smoke Alarms for the Deaf, Deafened or Hard of Hearing

Both the Ontario Building Code and Ontario Fire Code require the installation of smoke alarms in residential occupancies. By definition, a smoke alarm must sound an audible alarm to alert the home’s occupants. Unfortunately, an audible alarm may not alert an individual who is deaf, deafened or hard of hearing.

There are numerous smoke alarms available on the market today that address the specialized needs of these individuals. Some devices utilize a bright flashing strobe light, as well as an audible alarm, to alert the residents in the event of a fire. Due to the electrical supply requirements to operate these strobe lights, they must be wired directly into the home’s 110v A/C electrical system. Some models have a 9v battery backup that will ensure the audible alarm will activate in the event of a power failure, however the battery will not activate the strobe light.

Additional options also exist that allow the individual to connect their smoke alarms to an alerting system that may incorporate a flashing strobe light, vibrating pager and/or vibrating bed shaker to alert the resident to the emergency. Other suitable options are also available.

A catalogue detailing all available options for the deaf, deafened or hard of hearing is available through The Canadian Hearing Society. You can contact The Canadian Hearing Society by calling 519-253-7241 (TTY: 519-254-1704). Their Head Office contact numbers are 1-800-465-4327 (TTY: 1-800-537-6030) and their website is

Smoke Alarms featuring “HUSH” Control Feature

Cooking vapours and steam can sometimes activate a smoke alarm when no fire emergency is present. These are considered nuisance alarms and are the primary reason for people illegally disabling their smoke alarms by removing batteries or disconnecting the power supply to their smoke alarms. This practice of disabling a smoke alarm is extremely dangerous and against the law!

Smoke alarm manufacturers offer smoke alarms with a “HUSH” or “PAUSE” feature that allows the resident to temporarily silence the nuisance alarm. Generally, the HUSH feature will silence the alarm for approximately 7 minutes and then automatically reset itself. The smoke alarm will indicate that it is in HUSH mode by use of a periodic “chirp” or a visual indicator, such as a flashing LED light.

NOTE: Dense smoke will override the “HUSH” control feature and sound a continuous alarm to alert you to a fire emergency.

CAUTION: Before using the “HUSH” feature, identify the source of the smoke and be certain a safe condition exists.

Ontario Fire Code Requirements for Smoke Alarms

The Ontario Fire Code requires all single family, semi-detached and town homes in Ontario, whether owner-occupied or rented, have a working smoke alarm on every storey of the residence and outside all sleeping areas. Failure to comply with the Ontario Fire Code smoke alarm requirements could result in a ticket of $360 or a fine of up to $50,000 for individuals or $100,000 for corporations. The Ontario Fire Code specifies that “no person shall disable a smoke alarm so as to make it inoperable”. This includes, but is not limited to, removing the battery. A tenant, or any other person, who disables a smoke alarm is guilty of a provincial offence and may be subject to a fine.


Homeowners are responsible for installing and maintaining smoke alarms.


Landlords are responsible for ensuring their rental properties comply with the law. They must also provide tenants with a copy of the smoke alarm manufacturer’s maintenance instructions.


Tenants of rental properties should contact their landlord immediately if their occupancy does not have the required number of smoke alarms, or if there are any problems or concerns with the alarms.

Smoke Alarm Installation

  • The Ontario Fire Code requires all single family, semi-detached and town homes in Ontario, whether owner-occupied or rented, have a working smoke alarm on every storey of the residence, including the basement and outside all sleeping areas. Smoke alarms are not required in individual bedrooms unless required by the Ontario Building Code at the time of construction. However, to help ensure ultimate protection, we encourage smoke alarms be installed in each bedroom within the residence. Where bedroom doors are closed at night, smoke alarms should be installed in each bedroom.
  • One smoke alarm is required to be installed in each storey of a home and adjacent to any sleeping areas within the home. As illustrated below, a storey can consist of more than one level. When a home contains multiple sleeping areas, a smoke alarm must be installed to protect each separate sleeping area. This may necessitate additional smoke alarms on some levels of a split-level home. The following illustrated example of a split-level home, indicating required smoke alarm placement, is provided for clarification. Note that since smoke rises, the smoke alarm serving the 1st storey is installed in the upper level of that storey.
  • ALTERNATE WORDING: One smoke alarm is required to be installed in each storey of a home and adjacent to any sleeping areas within the home. When a home contains multiple sleeping areas, a smoke alarm must be installed to protect each separate sleeping area. In some home construction, such as with split-level homes, a storey may consist of more than one level. Normally, one smoke alarm would suffice to serve both levels of a split-level storey, except in the case where both levels contain separate sleeping areas. In that instance a smoke alarm must be installed on both levels containing sleeping areas.The following illustration of a split-level home and the required smoke alarm installations is provided for clarification.
where to install a smoke alarm
smoke alarms on two story house

NOTE: Both the upper and lower levels of the 2nd storey require smoke alarm installation due to separate sleeping areas contained on both levels. However, only one smoke alarm is required to service both the upper and lower levels of the 1st storey since neither level contains a sleeping area. Also note that since smoke rises, the smoke alarm serving the 1st storey is installed in the upper level of the 1st storey.

Installation Tips

  • Read and familiarize yourself with the manufacturer’s instruction manual. Always follow the manufacturer’s instructions for installing, testing, and maintaining smoke alarms.
  • Smoke, heat and combustion products rise to the ceiling and spread horizontally. In order for the smoke alarm to properly sense the presence of smoke, the ideal location is on the ceiling in the centre of the room. Ceiling mounting is preferred in ordinary residential construction.
  • When installing the smoke alarm on the ceiling, ensure it is a minimum of 10cm (4 inches) from any wall.
  • If wall mounting is necessary, use an inside wall, ensuring it is a minimum of 10cm (4 inches) below the ceiling, but no lower than 30.5cm (12 inches) below the ceiling.
  • If the hallway serving the bedrooms is more than 9 metres (30 feet) long, install smoke alarms at both ends of the hallway.
  • Install smoke alarms at both ends of a room if it is more than 9 metres (30 feet) long.
  • In stairways with no doors at the top or bottom, install smoke alarms anywhere in the path of smoke moving up the stairs. However, always install smoke alarms at the bottom of closed stairways, such as those leading to the basement. Dead air trapped near the closed door at the top of the stairway could prevent smoke from reaching the smoke alarm if installed at the top of the stairway.

Locations to Avoid

  • Do not install smoke alarms in “dead air pockets”, for example within 10cm (100mm – 4 inches) of where a ceiling meets a wall or a corner of a room.
smoke alarm locations to avoid
smoke alarm locations to avoid
smoke alarm locations to avoid
  • Do not install a smoke alarm within 1 metre (3 feet) of a doorway to a kitchen or bathroom, forced air ducts used for heating or cooling, ceiling or ventilation fans, air conditioner units or other high airflow areas.
  • Do not install the smoke alarm where drapes or other objects may block the sensor.
  • Do not install in the peaks of vaulted ceilings, “A” frame ceilings or gabled roofs. For “A” frame type ceilings, install the smoke alarm 10cm (4 inches) below the peak. See the illustration below for clarification.
smoke alarm not vaulted ceilings
  • When installing a smoke alarm in a room with a sloped ceiling, position it 90cm (36 inches) horizontally from the highest point, as illustrated below, since dead air at the peak may prevent smoke from reaching the unit.
smoke alarm dead air space
  • Electronic “noise” may cause nuisance alarms. Install smoke alarms at least 30 cm (12 inches) away from fluorescent lighting. Avoid excessively dusty, dirty, greasy or insect-infested areas. Dust particles and insects may cause nuisance alarms or failure to alarm.
  • Do not install in areas where the temperature is colder than 4.4ºC (40ºF) or hotter than 37.8ºC (100ºF). Extreme temperatures may adversely affect the sensitivity of the alarm, as well as diminish the lifespan of the battery, if so equipped.
  • Do not install in areas where the relative humidity is greater than 85% or within 3 metres (10 feet) of showers, saunas, dishwashers or any other steam-producing appliance. Very humid areas along with steam can cause unwanted nuisance alarms and adversely affect the battery, if so equipped.
  • Do not install smoke alarms in your garage. Combustion particles produced when you start your automobile will cause unwanted nuisance alarms.

Dealing with Nuisance Alarms

  • Avoid installing smoke alarms in or near kitchens and bathrooms where steam or cooking are present
  • If a smoke alarm is installed within 6 metres (20 feet) of a cooking appliance it should be a photoelectric (optical) smoke alarm or one that incorporates a “HUSH” silencing feature;
  • Keep ovens and stovetop burners clean to eliminate minor smoke flare-ups;
  • Clean out accumulated crumbs from the bottom of toasters and/or toaster ovens and turn down the timer setting;
  • Use the kitchen vent hood fan, that exhausts to the outside, when cooking to remove steam and smoke during cooking;
  • Use bathroom ventilation fans, that exhaust to the outside, to remove steam build-up;
  • Relocate the smoke alarm from the ceiling to a spot on an adjacent wall;
  • Replace ionization type alarms with photoelectric (optical) alarms.
  • NEVER DISABLE A SMOKE ALARM BY REMOVING THE BATTERY OR SHUTTING OFF THE ELECTRICAL SUPPLY! If your alarm does not have a “HUSH” feature, use a towel or newspaper to fan the alarm to dissipate the smoke or steam.

Additional Smoke Alarm Information

Testing and Maintenance of Smoke Alarms

  • Read and familiarize yourself with the manufacturer’s instruction manual. Always follow the manufacturer’s instructions for installing, testing, and maintaining smoke alarms.
  • Ensure the smoke alarm is secure and unobstructed.
  • Test all smoke alarms monthly by pressing the “TEST” button. Pick a familiar, meaningful date to help remind you each month, such as a birth date or anniversary. A broom handle or cane can be used to depress the test button eliminating the need to climb a ladder or stand on a chair.
  • Test all smoke alarms after being away from home for more than 3 days (alternate 7 days). The low battery “chirp” may have activated while you were away from home and the battery is dead, leaving you without protection.
  • Once a year test your smoke alarms with smoke from a smouldering incense stick or a smouldering cotton string placed in an ashtray or other suitable noncombustible container. CAUTION: Smouldering materials used in this test should be disposed of in a manner that does not create a fire hazard. No open flames from matches, lighters or candles should ever be used to test smoke alarms. Doing so may damage the smoke alarm as well as start a fire in your residence.
  • Install a fresh battery in your smoke alarms at least once a year or whenever the low-battery warning sounds. Fire Prevention Week, which is the week of Thanksgiving, is an ideal time of year to replace your batteries annually.
  • For proper operation, smoke alarms must be kept clean and free of dust, cobwebs, etc. Never clean your smoke alarms using water, solvents or cleaners as they may damage the unit. Be sure to follow the manufacturer’s cleaning instructions at all times. Clean your smoke alarms by gently vacuuming them using the soft brush attachment on your vacuum. For battery-operated smoke alarms vacuum the outside only; do not try to open the unit. For electrically connected (direct-wired) smoke alarms, disconnect the power to the unit, open the alarm cover and gently vacuum the inside of the alarm, and then reconnect the power supply to the alarm. This cleaning should be done at least twice a year. Test your smoke alarm after cleaning to ensure it’s working. (OFM SITE – AC powered smoke alarms should only be vacuumed externally and no attempt should be made to open the case. Be sure to follow the manufacturer’s instructions at all times. If specifically recommended by the manufacturer, open the battery cover on battery operated smoke alarms and gently vacuum the circuit board.)
  • Clean the exterior of the smoke alarm to remove dirt and grease following the manufacturer’s instructions. Most manufacturers suggest using a damp cloth only.
  • Never paint a smoke alarm. Paint can seal the vents and interfere with the sensor’s ability to detect smoke, hampering its proper operation.
  • Replace smoke alarms if they fail to operate properly when tested.
  • Replace smoke alarms every 10 years from the date of manufacture. The date of manufacture is noted on the smoke alarm.

Children and Smoke Alarms

Ensure that your children recognize the sound of your home’s smoke alarms and know what to do when they hear that sound. Develop and practise a home fire escape plan with your family.

Research has shown that children tend to sleep much more deeply and longer than adults. The sound of a smoke alarm may not penetrate the deep sleep patterns of children. As children can be “deep sleepers”, caregivers should never assume that activated smoke alarms would awaken and alert their sleeping children. As part of their home fire escape plan, caregivers must make it their responsibility to awaken and evacuate children in the event of a fire.You may have recently seen news reports on television showing children sleeping through the sound of smoke alarms, but awakening rather quickly to the sound of a familiar, abrupt voice coming from a smoke alarm with voice recording capabilities. Although smoke alarms with voice recording capabilities may seem like a good idea, the Ontario Fire Marshal’s Office is not aware of any voice recording smoke alarms that have met the Canadian standard for smoke alarms, CAN/ULC-S-531, Standard for Smoke Alarms, or that they will consistently awaken sleeping children. We understand that Underwriters Laboratories (UL) is currently reviewing this product, and that Underwriters Laboratories of Canada (ULC) approval will be sought in the future.

Anyone who purchases one of these alarms should use discretion when recording a message. It is important that the message be applicable to any and all fire situation.

Disposal of Smoke Alarms

Residential ionization smoke alarms contain an extremely small amount of radioactive material, americium 241 (33 kilobecquerel – kBq). This is comparable to the background radiation already present in many materials.

The Canadian Nuclear Safety Commission has confirmed that individual smoke alarms containing americium 241 may be disposed of in the regular garbage. However, if the smoke alarm contains radium or if there are large numbers of smoke alarms to be disposed of, more than 10 units, they should be shipped to the Low Level Radioactive Waste Management Office for disposal. Their contact number is 613-998-6748.