Over 100,000 of these fans were issued to British troops on the Western Front during the First World War. Invented by Mrs Hertha Ayrton, a civilian scientist, they were used to clear the gaseous residue that collected in shell-holes and craters after a gas attack.
You didn’t fan the gas because it turned into a sludge that coated everything on the battlefield. Like sticky soda residue on everything but it kills you.
Chlorine and others were certainly gases.