Types of Smoke Alarms
Ionization smoke alarms best detect fast flaming fires. This type of alarm uses a small amount of radioactive material to "energize" or "ionize" the air, allowing the air particles to flow from two oppositely charged plates in the smoke alarm. During normal operation, without smoke present, the ionized air moves in a straight line from one plate to another. However, once smoke enters the chamber, this circuit is disrupted. The alarm recognizes this break in the circuit and reduction of the current, resulting in the activation of the alarm.
Photoelectric smoke alarms are less sensitive than ionization smoke alarms, and work on the basis of a slow, smoldering, thick black smoke producing fire.
In a photoelectric smoke alarm, rather than using a radioactive material, these alarms use a light source. As smoke enters the alarm chamber, the thick black smoke deflects the light to a sensor. When this happens, the alarm is sounded.
Placement of Your Smoke Alarm is Important
The placement of your smoke alarm is of paramount importance, and increases the response time you and your family have to get out of your home during a fire.
When installing your smoke alarm, follow the manufacturer’s instructions. Generally speaking, smoke alarms should be placed within 5 metres of all sleeping areas. This can include a common hallway to all bedrooms. Alternatively, a smoke alarm can be installed inside each bedroom; however, it is important to remember that the bedroom door should be closed at night to reduce smoke from entering quickly in the case of a fire.
Smoke alarms are most effective when placed on the ceiling, no less than 4 inches away from any walls, bulkheads, or obstructions.
Testing a Smoke Alarm
Smoke alarms should be tested according to the manufacturer’s instructions. Generally, most smoke alarms need to be tested every six months by pressing the "Test" button. Also, it is good practice to test the smoke alarm with smoke that can be created by blowing out a candle, or match.
Maintenance of a Smoke Alarm
To ensure your smoke alarm is effective, ensure that:
- batteries are replaced every 6 months, or every time you change your clocks
- smoke alarms are free from dust, paint, spray-on insulation