The Hekatron ORS-142-EX optical smoke switch works on the principle of scattering light. A light source and light sensor inside the sensing chamber are arranged in a way that light normally does not reach the sensor. Only when particles are suspended in the air, light is scattered on the receiver. The evaluation electronics in the ORS-142-EX monitors the smoke component of the sensor for mild contamination, serious fouling and for faults. The optical indicator shows the current operating status of the ORS-14-EX.