Incendiary bomb cooling down. (Preliminary Fire Extinguishing with Jet from Stirrup Hand Pump). Much damage may be caused in an air raid by light incendiary bombs. The intense heat and smoke from such a bomb and the fire which it will have started make close approach impossible until the atmosphere has been cooled down and the fire partly extinguished. This is done with a jet of water from a hose not less than 30 ft. long. The stirrup hand pump (illustrated and described on Card No. 18) is recommended for this purpose. The girl in the picture is kneeling, as smoke is not so thick close to the ground. Note Redhill container in foreground (see Card No. 17). (No.14)
Notes
 The caption is not quite clear about the use of a jet of water to control an incendiary bomb. The nozzle of the approved stirrup pump hose was adjustable to produce either a solid jet or fine spray, controlled by a sliding plate. The nozzle is shown at left, set to spray. Pushing the button seen on the left would slide the plate across, making the nozzle aperture larger, creating a jet. The jet was for use against normal fire, the spray for burning incendiary bombs. If a jet was used on a bomb, it would scatter burning drops of molten magnesium with the risk of them hitting the operator and setting fire to any combustable material they landed on. The original procedure was to use the jet first to put out fires caused by the bomb, and to cool the atmosphere before using the spray on the bomb itself. However, experience later proved that if the risk was minimal, then using the jet on the bomb was better, as it burned it out quicker, and burning magnesium was found to bounce off the skin without burning it. Using water on an incendiary bomb did not extinguish it; in fact, the aim was to cause the bomb to burn out faster, thus eliminating the risk of further fires. The water contained hydrogen and more oxygen for the bomb to consume, causing it to burn out in about a minute as opposed to the 10-15 minutes the bomb would burn for if left unchecked. About 5-6 gallons of water were required to deal with an incendiary bomb and any fires it might have caused.
References
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