An optical smoke sensor specifically designed for use in ventilation ducting. A venturi probe samples the air in the duct for smoke. Detector housing is mounted externally to the duct. This device can trigger the shut-down of an air-conditioning or ventilation plant to prevent the spread of smoke. Unfortunately air ducts do not just guarantee fresh air but in the event of a fi re they can also deliver toxic smoke from the fi re source to distant area via the exhaust air system. Therefore air ducts must be monitored. The Honeywell Gent duct sensor housing offers effective protection, which is easy to install and maintain. The Gent duct sensor housing is supplied complete with an S Quad Sensor base and is thus compatible with the full range of S-Quad detectors (S4-911 in high sensitivity state is recommended). The housing is mounted on the outside of the air duct. A Venturi pipe (0.6m, 1.5m or 2.8m) is inserted into the duct and delivers air from the duct through detection chamber and back to the duct. An air fl ow indicator shows whether there is an airfl ow through the housing. A maintenance hole in the transparent cover allows test spray to be applied without opening the cover. Using the Venturi effect means that a single sampling tube can be used and air velocities of as little as 1 Metre a second can be sensed. A mounting bracket is also available to mount the detector on circular and insulated ducts. The housing can be mounted in any orientation. The arrow shape design can be mounted in any orientation. The arrow shape design of the tough grey abs housing shows the direction of fl ow, thus making installation quick and simple.