Designed to prevent the recirculation or spread of smoke by air handling systems, fans, and blowers, Space Age Electronics' SL-2000 Series SMOKE DUCT DETECTORS feature Low-Flow Technology (100–4000 ft/min), no-tools-required front/rear loading/removing sampling/exhaust tubes, and test port valves for aerosol smoke testing without cover removal. They also interconnect (up to 30 units) for common functions, have magnet test capabilities (magnet included), and come with green pilot and red alarm visual indicators as well as four sets of Form “C” alarm contacts and standard interchangeable plug-in UL268 photoelectric or ionization heads. CSFM listed.