The Simplex 4098-9755 is a compact addressable duct smoke sensor housing designed for detecting smoke within HVAC duct systems. It includes a factory-installed 4098-9714 TrueAlarm photoelectric smoke sensor and operates using IDNet or MAPNET II two-wire communications, which also supply its operating power.

This model provides intelligent analog sensing, digitally transmitting sensor data to the fire alarm control panel for analysis, environmental compensation, and programmable sensitivity management. The control panel determines alarm thresholds, monitors sensor dirt accumulation, logs peak activity, and performs automatic calibration checks to reduce nuisance alarms.

The 4098-9755 does not include relay outputs (basic housing model). A clear polycarbonate cover allows visual inspection, and built-in test ports enable functional smoke testing without removing the cover. Sampling tubes are ordered separately and selected based on duct width.

This duct housing is UL listed to UL 268A for duct applications and is intended as a secondary detection device within HVAC systems, not as a substitute for open-area smoke detection.