Apollo 55000-317APO Series 65 Optical Smoke DetectorThe Series 65 Optical Smoke Detector uses light sensing technology to see smoke entering the chamber. The external detector molding is identical to that of the ionization detector, and has an indicator LED which is clear in quiescent state and produces a red light in alarm. Responds well to slow burning, smoldering fires Well suited to bedrooms and escape routes Unaffected by wind or atmospheric pressure Flashing LED and magnet operated test switch