An assembly for treating gaseous emissions has a substrate along which extend cells for the passage of emissions gas. Lengths of conducting wire are located in a set of the cells and an induction heating coil is used to generate a varying electromagnetic field, so as to inductively heat the lengths of conducting wire. The substrate body has a front for entry of flowing emissions gas to be treated into the substrate body and a back for exit of treated gaseous emissions gas. The lengths of conducting wire have projections extending from the front and/or back of the substrate body so that when inductively heated, the wire parts in the substrate body heat the surrounding substrate and the wire projections heat the flowing emissions gas directly.