The HM/PSE optical smoke detector has two integral red LEDs that provide 360° local visual indication of the device status. The photoelectric smoke sensor delivers high responsiveness, reduced sensitivity to dust and false alarms resulting from ingress of insect and other debris. The plug-in unit uses sophisticated processing circuitry that incorporates smoothing filters to help eliminate transient environmental noise conditions that can be the cause of unwanted alarms. The devices are managed by embedded software running complex algorithms that further improve resilience to false alarms and improve detection speed.