A reactor for the plasma-assisted processing of gaseous media, comprising a reactor chamber including a gas permeable bed of an active material, conduits for constraining a gaseous medium to flow through the bed of active material, wherein the bed of active material comprises a matrix array of components of dielectric material, wherein the matrix array comprises a plurality of first wire or rod form electrically conducting members interspersed with a plurality of second wire or rod form electrically conducting members, the first and second electrically conducting members being in electrical contact with and enveloped by dielectric material, the plurality of first electrically conducting members being connected together for connection to a first electrical supply terminal and the plurality of second electrically conducting members being connected together for connection to a second electrical supply terminal.