Equally valuable work was performed in the perfection of two carbon monoxide absorbents for the Navy. The better of these consisted of a mixture of suitably prepared oxides which acts catalytically under certain conditions, and causes the carbon monoxide to react with the oxygen of the air. Since there are color changes connected with the iodine pentoxide reaction (the first absorbent) it has been possible to develop this so as to serve as a very sensitive detector for the presence of carbon monoxide in air. While the question of smoke filters was so important that it occupied the attention of several Sections, the Defense Section developed, as a part of its work, a standard method of testing and comparing filters, and did a great deal of work on the preparation of paper for this purpose. Various problems related to mustard gas were also studied. The question of a protective ointment was solved as successfully as possible under the circumstances, but was dropped when it appeared doubtful if under battlefield conditions of concentration and length of exposure, any ointment offered sufficient protection to pay for the trouble of applying it. The removal of mustard gas from clothing was investigated, especially by the accelerating effect of turkey red oil. Another phase of the work concerned the destruction of mustard gas on the ground, while a fourth phase related to the persistency of mustard (and other gases) on the field of battle. The Gas Mask Research Section concerned itself largely with developing methods of testing canisters and with routine tests. When one considers the number of gases studied experimentally, the large number of experimental canisters developed, all of which were tested against two or more gases, and further that the Section assisted in the control of the production at Long Island City, it is seen that this was no small job. In addition, the effect of various conditions, such as temperature, humidity, ageing, size of particles, were studied in their relation to the life of absorbents and canisters. Man tests and mechanical tests will be discussed in a later chapter. Other studies were concerned with weathering tests of gas mask fabrics, mustard gas detector, and covering for dugout entrances (dugout blankets), which were impregnated with a mixture of mineral and vegetable oils. In studying the course of gases through a canister the “wave front” method was of great value in detecting defects in canister design and filling.