It looks like French and German gas mask designs during WW1 both featured canisters mounted on the 'nose' of the mask itself, while British masks had a hose to a body-mounted filter.
Did one design have any innate advantages over the other? It seems like a hose might be more vulnerable to getting snagged on things, but a filter canister hanging off the face seems more unwieldy.
The French used the M2 mask, basically a hood that was impregnated with chemicals to absorb gas, like the British smoke hood. It was mostly used for weaker gasses like tear gas and chlorine. The german gm15 was better because it actually used a filter. The British small box respirator (sbr) was by far the best designed. It contained a box that the hose connected to, that contained charcoal, cotton, and other gas absorbing materials. The sbr could be used for up to about 7 hours before the lenses fogged up. The biggest disadvantages of the sbr was that they were very uncomfortable. They have nose clips that hold the nose closed to avoid breathing in any air, and you had to bite down on a mouth piece to breath though, like on a snorkel.