Activated charcoal will be used in war as an absorber in filters, both in personal gas masks and in air-inlets into buildings. Its granules may be swallowed with water to wash out the digestive system after several types of poisoning. The principal manufacturers of charcoal in Britain are J.L.Bragg (Ipswich) Ltd., of 34 Boss Hall Road, Ipswich, Suffolk.
During a refuge period rough charcoal will serve as a fuel which burns with considerable heat but no smoke and, as a non-conductor of heat, for insulation around coolstores.
Charcoal is made by heating seasoned wood or certain other organic materials where there is insufficient air for their complete combustion. A wooden post is held vertical by being sunk a few inches into the ground. Upright round this is placed a circle of logs. Further logs are leaned slightly against the first ones, and then more round these getting shorter all the time. This continues until a wooden hemisphere has been built, which is then covered with a layer of turf. Leaned inwards against the turf is an outer circle of logs. Next, round and over all this is shovelled a thick layer of soil and leaves. This makes the pyre, the diameter of which should be about three times its height, fairly airtight.
Finally, the original post is pulled out. Into the hole left by it are dropped burning charcoals and kindling. When the logs round the kindling have begun to burn strongly, the hole in the top centre of the pyre is sealed. The time the wood must be left depends on the quantity. A mound 15 ft. across will take about 10 days.