'Rendering Your Refuge Room Gas- Proof', Wills cigarette card, 1938.
© Science Museum / Science & Society Picture Library
One of a series of 'Air Raid Precautions' cards. Arrows indicate all the spaces where gas could seep into a room; through gaps in window and door frames, floorboards, chimneys and air vents. Despite widely being regarded as a useful source of instruction, production of cigarette cards was halted during both World Wars due to shortages.