The SSU-SL-701 DUCT CARBON MONOXIDE DETECTOR KIT, from Space Age Electronics, features a replaceable snap-in sensor, Test Mode for aerosol CO testing, historical/retrievable reporting data, and front/rear loading sampling/exhaust tubes. It performs a self test every 24 hours and is connectible with to up to 30 other units. Kit includes: SL-701 Detector, Fast Tube Sampling Tubes, and MSR-50/CO Remote accessory.