<P> The earliest military uses of chemicals were tear - inducing irritants rather than fatal or disabling poisons . During World War I, the French army was the first to employ gas, using 26 mm grenades filled with tear gas (ethyl bromoacetate) in August 1914 . The small quantities of gas delivered, roughly 19 cm3 per cartridge, were not even detected by the Germans . The stocks were rapidly consumed and by November a new order was placed by the French military . As bromine was scarce among the Entente allies, the active ingredient was changed to chloroacetone . </P> <P> In October 1914, German troops fired fragmentation shells filled with a chemical irritant against British positions at Neuve Chapelle, though the concentration achieved was so small that it too was barely noticed . None of the combatants considered the use of tear gas to be in conflict with the Hague Treaty of 1899, which prohibited the launching of projectiles containing asphyxiating or poisonous gas . </P> <P> The first instance of large - scale use of gas as a weapon was on 31 January 1915, when Germany fired 18,000 artillery shells containing liquid xylyl bromide tear gas on Russian positions on the Rawka River, west of Warsaw during the Battle of Bolimov . However, instead of vaporizing, the chemical froze and failed to have the desired effect . </P> <P> The first killing agent used by the German military was chlorine . Chlorine is a powerful irritant that can inflict damage to the eyes, nose, throat and lungs . At high concentrations and prolonged exposure it can cause death by asphyxiation . German chemical companies BASF, Hoechst and Bayer (which formed the IG Farben conglomerate in 1925) had been producing chlorine as a by - product of their dye manufacturing . In cooperation with Fritz Haber of the Kaiser Wilhelm Institute for Chemistry in Berlin, they began developing methods of discharging chlorine gas against enemy trenches . </P>

When did germany first use poison gas in ww1