As gas warfare developed not only were all kinds of gas shells sent over in a bunch but they were accompanied by high explosive, shrapnel and anything else in the way of trouble that the enemy possessed. A man near the front line, under those conditions, had all he could do and frequently more than he could do, to get his mask on and keep it on while doing his bit. Consequently he had no time, even if he had the inclination, to record how long he had the mask in the various gases. In this connection, after the Armistice was signed we in the field were requested to obtain for experimental purposes 10,000 canisters that had been used in battle. Each was to be labeled with the length of time it had been worn in or out of gas, and if in gas, the name of each gas and the time the mask was worn in it. This request is just a sample of what is asked by those who do not realize field conditions. One trip to the front would have convinced the one making the request of the utter impossibility of complying with it, for really no man knows how long he wears a mask in gas. With gas as common and as difficult to detect (when intermingled with high explosive gases and other smells of the battle field) as it was at the end of the war, each man wore the mask just as long as he could, simply as a matter of precaution. Before hostilities ceased we were trying out a method of calling in say fifty canisters per division once a week for test in the laboratory. If the tests showed the life of the canisters to be short new canisters would be issued. While we did not have opportunity to try out this plan, it gave promise of being the best that could be done. With gas becoming an every day affair, the only other alternative would seem to be to make issues of new boxes at stated intervals. On the other hand there are no definite records of casualties occurring from the exhaustion of the chemicals in the box. Undoubtedly some did occur, but they were very, very few. In nearly all cases the masks got injured, or the box became rusted through before the chemicals gave out. TONNAGE AND NUMBER OF MASKS REQUIRED It will probably be a shock to most people to learn that with more than two million men in France we required nearly 1500 tons of gas material per month. This tonnage was increasing, rather than decreasing, to cover protective suits, gloves, pastes, and chloride of lime, as well as masks. The British type respirator was estimated to last from four to six months. The active part of the war, in which the Americans took part, was too short to determine whether this was correct or not. The indications were, however, that it was about right, considering rest periods and fighting periods.