A B1 filter is a type of protective filter designed for respirators, such as half-masks or full-face masks. The "B" designation specifies that the filter protects against inorganic gases and vapours. These substances include, for example, chlorine, hydrogen sulfide, or hydrogen cyanide. The digit "1" indicates the filter's capacity class, in this case, low. The filter is therefore suitable for short-term use or for working in environments with a low concentration of harmful substances. B-type filters are standardly marked with a grey coloured stripe for easy identification.