… Other breathing appliances and gas masks, excluding protective masks having neither mechanical parts …
Explanatory notes
… appliances of a kind used by, for example, airmen, divers, mountaineers or firemen. These may be self‑contained … pipes, storage cylinders or (in the case of certain short distance apparatus) the outside atmosphere. This heading … poison gases). In these appliances air for breathing comes directly from the outside and is passed through a filtering …