Air-pollution filter and face mask

Claim 1

A filter which has a plurality of component elements which, in combination, provide means capable of passing a gas stream therethrough at a flow rate which, per circular section of about 5 centimeters in diameter, is in the range of from 50 ± 20 liters per minute at a pressure drop of at most about 4.0 centimeters of water, the elements comprising, in sequence: i. porous compressible means to filter contaminated gas and particulate activated charcoal means; ii. low-resistant prefilter means to retain particles and to protect subsequent elements; iii. low-resistant filter means for filtering particulate matter as small as 0.3 micron in diameter and moisture-trapping absorbent means; and iv. means to protect preceding elements; the particulate activated charcoal means being no further upstream than the porous compressible means; the moisture-trapping absorbent means being no further upstream than the low-resistant filter means; the porous compressible means providing means for removal of large dust particles, pollen grains, other particulate matter and aerosol droplets from the gas stream; the particulate activated carbon means providing means for removal of irritating gases from the gas stream; each element being immediately juxtaposed to adjacent elements; and the porous compressible means exerting sufficient positive pressure to maintain the particulate activated charcoal means in position.