Method of manufacturing a filter unit for an air purifying respirator and such a filter unit

A method of manufacturing a filter unit for an air purifying respirator, comprising:

• providing a sheet of filter material;
• feeding a portion of the filter material to an open mould of an injection moulding machine, which mould comprises two mould halves exhibiting a mould cavity and a corresponding mould geometry for forming at least one filter panel, an inlet wall panel and an outlet wall panel;
• closing the mould to thereby cut out at least one filter wall from the sheet;
• holding the at least one filter wall in said mould;
• forming, in said mould, a filter panel frame around each of the at least one filter walls by injection moulding a polymer material onto the at least one filter wall to form a filter panel;
• simultaneously, by injection moulding said polymer material into said mould, forming an inlet wall panel and an outlet wall panel as an integral piece with the at least one filter panel, wherein pairs of panels are mutually interconnected by a respective bridging portion;
• opening the mould;
• retrieving the inlet wall panel, the outlet wall panel, and the filter panel comprising the filter wall and the filter panel frame fixed to the filter wall;
• and
• folding the panels, at the bridging portions in a zig-zag configuration, into a stack of panels with the at least one filter panel being arranged between the inlet wall panel and the outlet wall panel.