Gent S4-901 CO Dual Optical DetectorThe Gent S4 901 CO Detector: Your Ultimate Guide What type of sensor does the gent s4 901 CO detector use? The Gent S4 901 CO detector uses a combination of dual optical and heat sensing elements to detect the presence of carbon monoxide in the air. This unique sensor combination includes both optical forward scatter and optical backward scatter technology, making it highly effective at detecting even the smallest amounts of CO. As a Honeywell Vigilon