Abstract: The invention provides a method of making a filter for use in venting a colostomy or ileostomy bag. An assembly comprising a first sheet of a gas permeable and water impermeable material, a second sheet of material which is gas permeable or is rendered gas permeable by the provision of at least one aperture therethrough, and a sheet of carbon cloth between the first and second sheets is fed to a sealing station. In the sealing station the assembly of sheets is sealed together, preferably heat sealed by a weld extending through the periphery of the carbon cloth, to form a filter comprising two pieces of the above mentioned first and second sheets with a piece of the carbon cloth sealed therebetween. The filter is then removed from the remainder of the assembly.