British troops conduct an anti-gas drill. Warnings are sounded by strombos horns to troops in trenches. Gas masks are donned. Gassed men are carried from trenches on stretchers. Phosgene detectors are used to test the air. Trenches are cleared with Ayerton fans. Masks are taken off and rifles cleaned. National Archives Identifier: 24626 Local Identifier: 111-H-1121.