Abstract: A self-propelled continuous mining machine which includes a mobile frame assembly having a material dislodging device, and a conveying system. A dust collecting system is positioned on the mobile frame assembly for inducing a flow of air through a duct system. As material is dislodged from a mine face, the dust collecting system draws airborne dust created by the dislodging device through the duct system and into the collecting system mounted on the mobile frame assembly. The duct system has two sets of vertical walls each connected to and spaced by a horizontal wall with one set of vertical walls fitting channel-like into the other set of vertical walls. The duct assembly has a gasket, seal or other means of preventing airborne dust from escaping through the two sets of vertical walls. The duct assembly is expandable to increase the capacity of the duct system.