The PAD300-DUCTR is designed and built to meet all local requirements, as well as the NFPA regulations regarding duct smoke detectors. Air sampling is accomplished by two (2) tubes which protrude into the duct. An exhaust tube of one (1) standard length (7") is supplied in the installation kit with the smoke duct unit. Once the duct width has been determined, the air intake sampling tubes must be ordered. Sampling tubes are supplied in three standard lengths: 2.5'., 5'., and 10'. and cut to size to fit the duct. Mounting the duct smoke unit is accomplished by the use of a template and two (2) sheet metal screws, which are provided. Mounting can be achieved without the removal of the clear cover which is secured by four (4) capture screws.