Prior to the start of the Second World War the British Government thought that German bombing would be more devastating than it actually was. They also thought that the Germans would use chemical warfare and drop gas bombs on British cities. An advisor to the government – Liddell Hart – told the government to expect 250,000 deaths in the first week of the war alone. The fears were not unreasonable. War gases had a terrible effect on soldiers in the First World War.
Children were evacuated from major cities, everybody was given a gas mask and information on war gases was issued.
In 1938 WA & AC Churchman issued a set of 48 cigarette cards dealing with Air-Raid Precautions. Fifteen of the cards dealt with precautions against gas attack.
The full set of cards.
The pamphlet below was issued by the Ministry of Home Security. Though the gases listed sound very nasty they were mainly of WW1 vintage and the advice was out of date. In the late 1930s the Germans had developed far deadlier gases, including the nerve agents tabun and sarin. Gas masks would not have been much use. Sarin can kill by being absorbed through the skin.
The same information was also distributed in the in the form of a wheel chart.