German forces launched first attack using gas on April 22 , 1915 . 50km of gas were used by German and Allied forces in WW1 . Around one million soldiers were exposed to gas and 90,000 killed . Prohibition of Chemical Weapons organisation to hold memorial event .
German forces launched first attack using gas on April 22 , 1915 . 150,000 tons of gas were used by German and Allied forces in WW1 . Around one million soldiers were exposed to gas and 90,000 killed . Prohibition of Chemical Weapons organisation to hold memorial event .