The P helmet, PH helmet and PHG helmet were early types of gas mask issued by the British Army in the First World War, to protect troops against chlorine, phosgene and tear gases. British Vickers machine gun crew wearing PH-type anti-gas helmets near Ovillers during the Battle of the Somme, July 1916 A World War I British P Helmet c.1915 PH-type helmet in Royal Canadian Regiment Museum.
