The SM-501 series duct smoke detectors will provide early detection of smoke and products of combustion present in the air moving through a duct in any commercial, industrial, or residential application. These devices are designed for the prevention of smoke re-circulation by the air handling systems, fans, and blowers. The SM-501 is designed and built to meet all local requirements, as well as the NFPA regulations regarding duct smoke detectors. Output terminals are provided for remote accessories such as horns, strobes, remote status indicators, and test/reset key switches or pushbuttons. Air sampling is accomplished via two tubes that protrude into the duct. An exhaust tube with a standard length of 7" is supplied in the installation kit with the unit. Once the duct size is determined, a sampling tube must be ordered. Four standard sizes including a 1', 2.5', 5', and 10' lengths can be ordered and cut to the correct size of the duct. The SM-501 provides (2) sets of 10A Form "C" alarm contacts, along with (1) set of 10A Form "C" trouble contacts for monitoring head removal and supply voltage failure. The green pilot and red alarm indicators provided on the front of the SM-501 signal the operating status of the device. A manual test/reset switch is located next to the LED indicators. (Use part number SM-501-N for ionization and SM501-P for photoelectric). The SM-501 is covered by ACI's Two (2) Year Limited Warranty. Early detection of smoke and products of combustion present in air moving through HVAC ducts in Commercial, Industrial, and Residential applications. Advanced detector head design yields internal dust filtering with no additional screens or filters to clean Easy mounting without cover removal Compact size