Salwico DOS 3 Optical Smoke Detector N1115 The Salwico DOS is a low profile conventional optical smoke detector. Salwico DOS3 is designed to combine optimal response to smoke with a strong immunity to false and unwanted alarms. Salwico DOS detector design provides strong immunity to air velocities, contamination and EMC. By means of a special protective mesh it is ensured that smoke can enter the detector easily whilst accessibility to insects and airborne contaminants is eliminated.