Gas filter with a Dräger-specific bayonet-type connector to be used with twinfilter half masks Dräger X-plore 3000 and twinfilter full facepieces X-plore 5500. - A1: protection against gases and vapours from organic compounds - B1: protection against inorganic gases and vapours (e.g. chlorine, hydrogen sulfide, hydrogen cyanide) Filter class 1 offers low protection and has a maximum permissible contaminant concentration of 0.1 Vol% (1000 ppm).