From verso of card: "The Civilian Anti-Gas Schools are provided by the Home Office. . . . The schools train anti-gas instructors for the public service, for local authorities and others. Sixty students are taken at a time, and the course lasts two weeks. The picture shows postal workers undergoing training. Those on the left, wearing oilskin coats and Civilian Duty Respirators . . . are women telephonists. The men on the right are being fitted with Service Respirators before going into the gas chamber."