A boy shows two other children how to put on a gas mask. (Photo by David Savill/Topical Press Agency/Getty Images). UK, 18th January 1937

Metropolitan Police Constables wearing gas masks line up to enter a mobile gas chamber at East Ham Police Station, London. This official gas training lesson is intended to give them valuable experience in the event of a genuine emergency. (Photo by David Savill/Topical Press Agency/Getty Images). 13th March 1937

A guard wearing a gas mask signals the go-ahead to an experimental anti-air raid train during a demonstration at Euston Station, London. The new LMS train has two coaches, one equipped with decontaminating apparatus and one intended as an ARP instructional unit. (Photo by J. A. Hampton/Topical Press Agency/Getty Images). 24th November 1937

Wearing protective suits and gas masks, members of the local Air Raid Precautions Decontamination Squad appeal for new volunteers outside the Council Offices in Esher, Surrey, (Photo by H. Allen/Topical Press Agency/Getty Images). 14th February 1938

London firemen testing the oxygen gauge on breathing apparatus at Southwark, south London. (Photo by Reg Speller/Fox Photos/Getty Images). 25th May 1936

A practical training session in bridge building during war time conditions, provided by the Royal Engineers, at a camp near Weymouth. (Photo by Fox Photos/Getty Images). 16th June 1937

Soldiers being instructed on how to use a smoke helmet by the CQMS fire-instructor at the Fire Brigade Station in Aldershot. (Photo by Fox Photos/Getty Images). 15th April 1936

Some of London's telephone operators and engineers, trying out their gas masks at the anti-gas civilian training centre in Gloucester, where they were taught how to deal with gas attacks. (Photo by Harry Todd/Fox Photos/Getty Images). 13th February 1937

London firemen acclimatising themselves to the breathing apparatus they sometimes have to wear during the course of duty. (Photo by Reg Speller/Fox Photos/Getty Images). 25th May 1936

A decontamination squad trained by the Corporation of the City of London to deal with gas attacks from the air. (Photo by Keystone/Getty Images). 23rd March 1937

A fireman wearing a gas-mask directing water on a house at Chatham, Kent, during an air-raid exercise. (Photo by London Express/Getty Images). 1938

A sergeant of the Grenadier Guard seen shouting orders through a gas mask. (Photo by London Express/Getty Images). 1938

A demonstration of gas masks and an anti-gas service van at the Public Health Exhibition in the Royal Agricultural Hall, London. (Photo by David Savill/Topical Press Agency/Getty Images). 16th November 1936

Westminster schoolboys making their way to school with an employee of the Westminster City Council taking final tests in and anti-gas course. (Photo by Watkins/Fox Photos/Getty Images). 5th February 1938

A team training at the Lancashire and Cheshire Coal Owners' Rescue station at Boothstown, Lancashire, apply artificial respiration to a 'survivor' during an exercise. (Photo by Arthur Tanner/Fox Photos/Getty Images). 13th May 1936

Brighton, Hove and Southern Railway police wearing gas masks. (Photo by Fox Photos/Getty Images). 24th November 1936

Sergeant Taylor of Blackburn Police adjusting his constables gas mask during a gas drill, 10th September 1936. (Photo by Fox Photos/Hulton Archive/Getty Images)