The XP95 Ionisation Smoke Detector uses a low activity radioactive foil to detect fires by irradiating the air in the smoke chambers causing a current flow. If smoke enters the chamber, the current flow is reduced leading to an alarm. The detector responds well to fast-burning, flaming fires and it is designed to operate in a variety of environments. It has minimal effects from the temperature, humidity, atmospheric pressure and is protected against electromagnetic interference over a wide frequency range.