Which smoke alarm is the right one to use?

The two most common types of smoke alarms used today: photoelectric alarms 
and ionisation alarms.

Ionisation smoke alarm is based on the principle of ion flow within a chamber. 
An alarm condition occurs when the ion flow is affected by smoke particles. This type of 
alarm is most effective to detect small particles of smoke.

Photoelectric smoke alarm is based on the principle of optical detection. It is also
known as the "scattered" light principle. An alarm condition occurs when smoke particles 
enter a light path and some of the light is "scattered" by reflection and refraction onto a 
sensor. This type of alarm is best for areas where dense smoke may occur, 
such as in ductwork.

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