40950 series Duct type smoke detectors sample and measure the air movements in the heating and ventilation ducts through the smoke detector in the enclosure with an air metering tube. The air in the channels can be sampled with the measurement / sampling tube / (measurement) tube, which expands from the detector housing to the canal. The length of the aluminum measuring / sampling tube can be shortened by the diameter of the channel. It can be fitted with a detector to work in dusty environments. Precision 40950-BR, the diameter of the 40950 housing is 100 mm. which can be as small as a rectangular shape and allows installation in circular channels.