Duct Smoke Detector Sensor Head Finish Smooth Ceiling Mounting Depth (In.) 4 1/8 in Height (In.) 2 in Ambient Temp Limits (F) -4 Degrees to 158 Degrees F Air Velocity (FPM) 4000 fpm Alarm State (mA) 135 mA Humidity Range ( Percent RH) 0 to 95 Percent RH Number Required 1 Standby State (mA) 65 mA Voltage 120V AC 24V AC Standards FM UL