First Gas Attack of the First World War. Chemical weapons had been outlawed by international treaties before the First World War. In the spring of 1915, however, Germany decided to test a new weapon — chlorine gas — on the Ypres salient. On 22 April 1915, the Germans released more than 160 tonnes of the gas from thousands of canisters arranged along German lines. The Canadians and the French-Algerian troops manning the trenches to their left watched as a mysterious yellow-green cloud appeared first over no man’s land between the opposing armies, and then drifted with the wind southward over the Allied lines.
The heaviest part of the gas cloud hit the Algerians, the chlorine burning their throats and causing their lungs to fill with foam and mucus, effectively drowning the men in their own fluids. The Canadians watched in shock and horror as the suffocating Algerians broke from their lines, many fleeing toward them in a panic — leaving a 6 km hole in the front lines on the Canadians’ left flank.
As German forces moved from behind the drifting gas cloud toward the now-empty Algerian trenches, Canadian and British battalions — including soldiers suffering from the gas — moved to plug the hole. During hours of desperate fighting that day, with help from isolated groups of French and Algerians, they managed to stop the enemy from encircling the First Canadian Division inside the salient, and from marching on the city of Ypres. This is how the First Gas Attack of the First World War happened. Read about Bombing of Hiroshima and Nagasaki. – Franklin D Roosevelt
*** Chlorine gas is a pulmonary irritant with intermediate water solubility that causes acute damage in the upper and lower respiratory tract. Occupational exposures constitute the highest risk for serious toxicity from high-concentration chlorine (see the image below). Mixing of chlorine bleach (sodium hypochlorite) with ammonia or acidic cleaning agents is a common source of household exposure. As with all poisons, the dose determines the toxicity. Exposure to low concentrations of chlorine for prolonged periods may have destructive effects, as might very short-term exposure to high concentrations.