The Edwards Signaling SD-T18 SuperDuct 18" Air Sample Tube is designed for convenient installation in tight spaces with a depth of less than 2". It features a PCB-mounted photoelectric sensor equipped with intelligent technology and patented differential sensing for stable and reliable environmental compensation. This tube supports high air velocity duct applications up to 4000 ft/min (20.3 m/sec) with a wide smoke sensitivity range from 0.79% to 2.46% per foot obscuration. Compatible with standard Kidde Intelligent detectors and the four-wire duct smoke detector SD-4WJ, it includes a prewired standard or relay detector base for easy installation. Upgrade your fire detection system with this efficient, reliable component today!