10Functional principle and features The smoke alarm device does not detect heat, gas, steam, fire orflames. People with impaired hearing may not be able to hear the alarm.Alarms with additional optical signalling are available for such cases. Particularly high electromagnetic radiation could impair the functionof the detector. For this reason, do not install the detector nearmagnets or devices which produce electromagnetic radiation. The smoke alarm device operates in accordance with the opticalprinciple (photoelectric reflection) and features a measurementchamber in which infiltrating smoke particles are measured. If the alarm threshold is exceeded, a loud acoustic alarm sounds. The alarm is switched off as soon as the measurement chamber isfree of smoke again.