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...