title: Gas mask
context: The German army used poison gas for the first time against Allied troops at the Second Battle of Ypres, Belgium on 22 April 1915.[17] As an immediate response was cotton wool wrapped in muslin issued to the troops by 1 May. This was followed by the Black Veil Respirator, invented by John Scott Haldane, which was a cotton pad soaked in an absorbent solution which was secured over the mouth using black cotton veiling.[18] Seeking to improve on the Black Veil respirator, Cluny MacPherson created a mask made of chemical absorbing fabric and which fitted over the entire head.[19] A 50.5cm ×48cm (19.9in ×18.9in) canvas hood treated with chlorine-absorbing chemicals, and fitted with a transparent mica eyepiece.[20]  Macpherson presented his idea to the British War Office Anti-Gas Department on 10 May 1915, with prototypes being developed soon after.[21] The design was adopted by the British Army and introduced as the British Smoke Hood in June 1915; Macpherson was appointed to the War Office Committee for Protection against Poisonous Gases.[22] More elaborate sorbent compounds were added later to further iterations of his helmet (PH helmet), to defeat other respiratory poison gases used such as phosgene, diphosgene and chloropicrin. In summer and autumn 1915, Edward Harrison, Bertram Lambert and  John Sadd developed the Large Box Respirator.[23] This canister gas mask had a tin can containing the absorbent materials by a hose and began to be issued in February 1916. A compact version, the Small Box Respirator, was made a universal issue from August 1916.
question: Who developed the first gas mask used in World War I?
answers: John Scott Haldane