When was the gas masks used inWW1 developed?

Gas masks used in World War I were developed in response to the widespread use of chemical weapons during the conflict, particularly following the first large-scale gas attack by the Germans at Ypres in April 1915. Early designs were created shortly after this event, with significant advancements occurring throughout the war. The British Army, for example, began issuing the first effective gas masks to troops in late 1915, which improved over time as more sophisticated designs were introduced.