Horse gas masks were first used during World War I to protect horses from harmful chemical agents. Horses were the primary mode of transporting men and material to war zones and needed protection from irritating chemicals like chlorine and phosgene, used during that time. Like most horse respirators, this mask was probably used in conjunction with a gas proof cape and leggings. The full head example is most likely post WWII and used for protecting horses against biological and chemical warfare. I’m not sure of this masks original origin. It’s full size and comes mounted on a modern horse head tack mannequin. We have just listed this pair of masks for sale on 1stdibs.