Types of Smoke Alarms

A smoke alarm is a battery operated or electrically connected device designed to sound an alarm when the presence of visible or invisible particles produced by combustion are sensed within the room or area in which it is located. There are two types of household smoke detectors in common use - ionization and photoelectric. Both possess strengths and weaknesses.

Ionization smoke alarms, the most common type in use and generally less expensive to purchase at $5 to $15, uses a small amount of radioactive material to ionize air in the sensing chamber. An alarm is triggered when a predetermined level of smoke particles enter the chamber. These detectors are generally more effective at detecting fast-flaming fires which consume combustible materials rapidly and spread quickly (paper burning in a wastebasket or a grease fire in the kitchen).

Photoelectric smoke alarms, priced between $30 and $40, are generally more effective at detecting slow, smoldering fires (cigarettes burning in couches or bedding) which smolder for hours before bursting into flame. They consist of a light emitting diode and a light sensitive sensor in the sensing chamber. An alarm is set off when the presence of suspended smoke particles in the sensing chamber causes the light beam to scatter.

While all detectors for sale in Canada must meet the standards of Underwriters' Laboratories Canada Inc. (ULC) - a non-profit safety-standards and testing organization - the two technologies operate on different principles and therefore respond differently to various conditions. Since you can't predict the type of fire that may occur, for maximum protection manufacturers recommend the use of both types of smoke alarms on each level of your home. Smoke detectors older than 10 years should be replaced with new ones.

The three major causes of home fires in Canada are cooking equipment, heating equipment and smoking materials. While fires caused by cooking equipment is the leading cause of Canadian home fires, fires caused by smoking materials kill more people than any other cause of fire.

Smoke alarms are not foolproof. They play a vital role worldwide in reducing the occurrence of deaths and injuries resulting from home fires. However, like any warning device, smoke alarms only work if properly located, installed, and maintained and smoke reaches them. The Office of the Fire Marshal of Ontario reports 85% of the cases where smoke alarms did not activate were due to dead or missing battery/power source.

Smoke alarms cannot operate without power ~ Do not remove or disconnect the power source. Use only batteries recommended by the manufacturer, test regularly for freshness and develop the habit of replacing with biannual time change.

Smoke alarms cannot detect fires if the smoke does not reach them ~ They may not detect fires on another floor or area of the home, in a remote area, in chimneys or walls, on roofs, or on the other side of closed doors. For maximum protection, install at least one smoke alarm on every level of your home, in every bedroom or sleeping area, and in every bedroom hallway

Smoke alarms may not be heard ~ Units which meets standards may not be audible through closed doors, above other activities, or by hearing or otherwise impaired individuals or sound sleepers. Special units should be installed for the hearing impaired

Smoke alarms may not have time to alarm before fire itself causes damage, injury or death ~ Due to the location or nature of the fire, smoke may not reach the unit immediately

Smoke alarms are not foolproof ~ Test detectors at least once a week to ensure in good working order

Smoke alarms have a limited life ~ Replace smoke alarms every 10 years. Replace immediately if not operating properly