serves as a gas filter that by absorption at least partially removes the noxious gases that are contained in the air inhaled application_number US 47609104 A description 0043 fig1 depicts a respiratory of filter 10 in a first embodiment it has an air permeable sleeve 11 four filter layers 12 and three air permeable separation layers 13 the sleeve 11 is made of a spun bonded nonwoven fabric that is produced from polypropylene fibers by melt spinning the nonwoven fabric is permanently charged electrostatically and has a weight per unit area of 30 to 40 g m 2 preferably 35 g m 2 each filter layer 12 is made of a rectangular piece of nonwoven fabric that has a width of 5 to 9 cm preferably 7 cm a length of 9 to 13 cm preferably 11 cm a thickness of 1 to 3 mm preferably 2 mm and a weight per unit area of 170 to 210 g m 2 preferably 190 g m 2 the nonwoven fabric of the filter layers 12 serves for one thing as a particle filter 20 and for another as a carrier for activated carbon which in turn serves as a gas filter the production of such active carbon filter mats is known in the prior art so it is not further described here each separation layer 13 is made of a rectangular piece of spun lace nonwoven fabric that has substantially the same width and length as the filter layers 12 a thickness of.