Duct Smoke Detector, Photoelectric, Finish Clear Plastic, Surface Mounting, Alarm Current 35 mA, Standby Current 25 uA, Depth 1 7/8 In, Height 5 7/16 In, Length 14 1/2 In, Ambient Temp Limits -20 to 158 F, Air Velocity 100 to 4000 FPM, Humidity Range 20 to 95 % RH, Standby State 25 mA, Voltage 20 to 31 VDC, 24V DC, 24V AC, 120V AC, 220/240V AC Fire Alarm Initiating DevicesWhen activated, devices send signals on a hardwired connection to initiate an alarm.Air Duct Smoke DetectorsActivate when combustion particles exceed 2.3% per ft. in air moving at 100 fpm to 4000 fpm. Match the air duct size to the appropriate air sampling tube. Remote Test/Reset Station 1EYC1 (sold separately) easily monitors difficult-to-access duct smoke detectors.All models are UL and C-UL Listed.Operating voltage: 24VAC/VDC or 120/240VAC