PHOTO TAKEN AT PHILADELPHIA CONTROL LABORATORY OF GAS DEFENSE DIVISION, SHOWING APPARATUS USED IN EXPERIMENTAL WORK ON THE EFFECT OF RESISTANCE TO INHALATION AND EXHALATION OF MASKS.
SIDE VIEW OF GAS CHAMBER AT CHEMICAL DEVELOPMENT LABORATORY, SHOWING SUBJECTS ON OUTSIDE BREATHING TESTS.
ANOTHER VIEW OF GAS CHAMBER AT CHEMICAL DEVELOPMENT LABORATORY, SHOWING SUBJECTS INSIDE.
All the rubber used was continually sampled and analyzed in the laboratories. The tensile strengths of all fabrics were determined by standard destructive tests. We also tested the adhesion of the rubber coating by standard chemical methods and worked out flexibility tests for the breathing tube.
After all of the factory inspection and material-control tests, the masks themselves were sampled and worn in highly toxic atmospheres. In this work thousands of our masks were worn by the officers and men of the Gas Defense Division in concentrated atmospheres of the most deadly gases. For such work we constructed testing rooms whose atmosphere could be completely exhausted and changed in 90 seconds. The efficiency of canisters was tested either by the lungs of the inspectors or by mechanical breathing into telltale solutions.
The story of the carbon (charcoal) which went into the American canister is one of the most interesting phases of the whole undertaking. Investigations carried on by the research staff of the National Carbon Co., aided by a clue from the University of Chicago, led to the selection of coconut shell as a raw material. Any carbon absorbs a definite number of times its weight of gas. Therefore the densest carbons will be most efficient, volume for volume, as gas absorbers in a given space. Coconut shells and other nut shells were found to be the most compact form in which carbon exists in nature in commercially practicable quantities, being considerably superior in this respect to anthracite coal and to such woods as ironwood and mahogany. Another essential for charcoal used in the canisters was that it must be so hard that it would not crumble easily and produce dust that would clog up the air passages and prevent easy breathing through the canister. Coconut shell fulfilled both of these conditions better than any other known material.