Tychem garments are tested against a broad range of hazardous materials to determine permeation which is critical for fabrics that are exposed to hazardous chemicals. Permeation occurs when a chemical is absorbed until it saturates one side of the material and then desorbs, or diffuses, to the other side of the material. By developing fabrics that pass these tests, DuPont helps protect first responders and industrial workers from hazardous liquids, vapors, gases and particulates.