Alarms employing ionisation technology generally sense fast burning fires more quickly than alarms employing photoelectric technology. Smoke alarms employing photoelectric technology generally sense smoldering fires more quickly than alarms using ionisation technology. While all smoke alarms have limitations, smoke alarms employing either ionisation or photoelectric technologies provide to the occupant reasonable notice of the presence of fire or smoke in the proximity of the alarm.

Note: When installing an alarm that is mains (AC) powered only, you should keep in mind that during a fire or CO event, if the circuit to which the alarm is connected is either not energised, or is compromised by the fire before sufficient smoke reaches the alarm to cause the alarm to sound, the smoke or CO alarm will not function and will not provide a warning of the fire or CO event.