“FACEPIECE OPERATIONS—The sewing machine operations were next performed. First the died out blanks were pleated to form the facepiece. The operator had to register the various notches in the blank to an accuracy of ¹/₃₂ in. and to locate the stitches in some cases as closely as ¹/₆₄ in. The band was next sewed to the periphery of the facepiece after which the harness was attached. The stitches on the outside of the facepiece were covered with liquid dope, which filled the needle holes and made the seams gas-tight. “In addition to the inspection of each operation, the completed facepiece was submitted to a control inspection to discover any defects that might escape the attention of the inspectors on the various operations. “ASSEMBLY OPERATIONS—The facepieces were now ready for assembly and were sent for insertion of the eyepieces, which was done in specially designed automatic presses. The eyepieces had to be carefully inserted so that the facepiece fabric extended evenly around the entire circumference. “Before manufacture began on a large scale, the most satisfactory method of conducting each assembly operation was worked out and the details standardized, so that operators could be quickly and efficiently trained. No detail was considered too small if it improved the quality of the mask. The assembly operations proceeded as follows: “The exhalation valve was first joined to the three-way metal tube which formed the connection between the facepiece, flexible hose, and mouthpiece. Each valve was then tested for leakage under a pressure difference of a one inch head of water. No valve was accepted which showed leakage in excess of 10 cc. per min. under these conditions. “The metal guard to protect the exhalation valve was next assembled, followed by the flexible hose. The three-way tube was then assembled to the facepiece by means of a threaded connection and the rubber mouthpiece attached. To illustrate the attention to details the following operation may be cited: “The contact surfaces between each rubber and metal part were coated with rubber cement before the parts were assembled. The connection was then tightly wired, care being taken that none of the turns of wire should cross and finally the wire was covered with adhesive tape so that no sharp edges would be exposed. “The masks, completely assembled except for the canisters, were inspected and hung on racks on specially designed trucks which prevented injury in transit, and were delivered to the Finishing Department. “CANISTER FILLING—Meanwhile the canisters were being filled, in another building.