Abstract: A method of assembly of a NBC Filter comprising a tubular formation of an inner filter medium closed at lease one end by a metallic inner end cap, a tubular mass of granulated carbon surrounding said inner filter medium to form an outer filter medium, a tubular mesh enclosing said outer filter medium, an annular, resilient gasket surrounding said inner end cap and an outer end cap of metallic material having a peripheral skirt which, in use, surrounds one end of the mesh tube while the gasket is compressed between the outer end cap and the carbon mass. A thixotropic adhesive is interposed between the inner periphery of the gasket and the inner end cap, between the outer periphery of the gasket and mesh tube and between the gasket and the outer end cap.