“World War I: a poisonous gas attack on the Canadians in Flanders, 24 April 1915. Coloured chalks by Louis Raemaekers.” [3702×5027]

Not a gas mask among them…..pee on a rag and breathe through it and hope for the best. Can’t imagine the terror, this image is a good capture of that.

[Source.](https://wellcomecollection.org/works/e3eydwj9?query=V0018241&wellcomeImagesUrl=GET%20/indexplus/image/V0018241.html%20HTTP/1.1)