Air in the dual sensing chambers is irradiated to produce ions that travel to the positive and negative electrodes, creating a current flow. As smoke enters the outer chamber, the flow drops and the voltage increases. The detector will then enter the alarm state and the indicator LED lights up.
An intergrating ionisation detector, suitable for use in areas where transient high levels of smoke may be expected, is also available.
Protector Alarms (UK) Ltd.