Gas resistant foam materials

An air and water permeable open cell solid flexible polyurethane foam resistant to the passage therethrough of noxious chemicals in liquid or vapor form, said foam having dispersed therein particulate activated carbon of average particle size in the range 7 to 10 microns and in an amount of at least 10% by weight of said foam and not in excess of 12 milligrams per sq. cm. of foam, said activated carbon particles being bonded in said foam by an acrylic elastomeric binder which is substantially free from substances which would substantially deactivate the activated carbon particles, said binder being present in an amount from 15 to 100 parts by weight per 100 parts by weight of said carbon.