We don't consider WP a chemical weapon, but an obscurant smoke device, the Russians consider it and all smoke chemical weapons. Now I realise that WP has some pretty devistating effect on human flesh as does other flame weapons like napalm. Interestingly the obscurant power of WP is primarily in the visual light spectrum, and it is difficunt to handle because the white phosphure has a low melting point and if the rounds aren't kept upright they will become unballanced and fly erratically. For these reasons WP is being replaced with red phosphorus which is easier to handle and has better obscurant properties in the IR spectrum, WP was only being used on an existing stock basis when I retired back in 1997, I doubt there is any left that hasn't expired.