Nurses in gas masks at the trenches, Germany, 1916. During WWI thousands of women served at home and overseas as Nurses working in military hospitals or in Casualty Clearing Stations closer to the battlefield. They provided vital skills and fulfilled an important role, one which is often overshadowed by the events on the battlefields themselves. The gas mask is a mask used to protect the wearer from inhaling airborne pollutants and toxic gases. The mask forms a sealed cover over the nose and mouth, but may also cover the eyes and other vulnerable soft tissues of the face. Some gas masks are also respirators, though the word gas mask is often used to refer to military equipment.