Method for making a filter cartridge that is suitable for attachment to a
respiratory mask. The method comprises the steps of (a) providing a mass
of filter material; (b) providing a filter cartridge housing that has an
inlet and outlet and a sidewall that includes sheet material; and (c)
thermoforming the sheet material of the housing sidewall around at least
part of the mass of filter material to place the housing sidewall in
direct contact with the mass of filter material to encapsulate the filter
material so that fluid is prevented from passing through the filter
cartridge from the inlet to the outlet without being filtered by the mass
of filter material.
