Smoke Alarm Guidelines

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.

• 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)

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.

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.

Advantages

• 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

Disadvantages

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

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.

Advantages:

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

Disadvantages:

• 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.