MIL-M-27274E(USAF)
4.6.6 Combination valve installation, exhalation resistance. The mask (with the combination valve installed) shall be placed on a suitable test stand. At an exhalation flow of 100 liters per minute, the pressure inside the mask shall not exceed ambient pressure by more than 4.67 millimeters of mercury.
4.6. 7 Delivery tube leakage. One end of the delivery tube shall be plugged and an air pressure of 5 pounds per square inch shall be applied to the other end. The tube shall be submerged just under the surface of water. Bubbles rising from the hose after 10 to 15 seconds of submergence shall be cause for rejection.
4.6.8 Delivery tube strength. One end of the tubing shall be attached to the combination valve mounted on the mask body. The other end shall be connected to a fitting simulating a connector conforming to MS27796. Clamps for the connections shall be of the type specified herein. One of the end connections shaIl be attached to a support. A weight of 63 pounds 1 pound shall be attached to the
other connection so that a straight pull is exerted on the tubing for a period of 3 seconds 2 seconds. The tubing shall not tear or separate from the end connections. The nylon anti stretch cord shall be attached during this test. Upon completion of this test the delivery tube shall be subjected to the test of (see 4.6.7).
4.6.9 Tear resistance. The tear resistance of the test sheets and sections of rubber cut from the sealing area of the facepiece shall be determined in accordance with ASTM-D-624-54, die B. Minimum tear resistance shall be 150 pounds per inch.
4.6.10 Hardness. The hardness of the test sheets and sections of rubber cut from the sealing of the facepiece in both the nose and check areas shall be determined in accordance with method 3021 of FED- STD-601, and shall have a shore A hardness of 45 5.
4.6.11 Toxicity. Toxicity shall be determined from the chemicals used in formation of the silicone rubber compound.
4.6.12 Subjective use. Objectionable odors, tackiness, and objectionable or detrimental performance characteristics shall be determined by subjective evaluation. The mask shall be used by human subjects at altitudes from ground level to 50,000 feet, at temperature from -40 F to + 160 F or any combination of such altitude and temperature for periods up to 2 hours. Subjective use tests are optional tests to be conducted at the discretion of and by the procuring activity when the mask appears to have performance characteristics or other properties which might be detrimental or objectionable for human use.
4.6.13 Hardshell flexibility. The hardshell shall be placed between the heads of a suitable compression testing machine with the heads contacting the sides of the hardshell at the point of maximum width. The hardshell shall be oriented so that dimension B (see figure 2) is parallel to the direction of movement of the heads. A suitable means of measuring the decrease in hardshell width under load shall be provided. The hardshell shall be deformed until failure or until the required decrease in width is attained, whichever occurs first. The rate of head travel shall be from 0.20 to 0.25 inch per minute. The hardshell shall withstand a decrease in width of at least 1 1/2 inches without visible cracking or breaking.
4.6.13.1 Special tool. A special compression tool for applying the load to the hardshell shall be used to minimize any effects caused by shifting of the test machine heads. This tool shall be constructed so
that loading is truly parallel to dimension B (see figure 2) and is applied through tool surfaces that are flat,
parallel, and perpendicular to dimension B (see figure 2).
4.7 Inspection of packaging. Except when commercial packaging is specified, the sampling and inspection of the preservation and interior package marking shall be in accordance with groups A and B quality conformance inspection requirements of MIL-P-116. The sampling and inspection of the packing for shipment and storage shall be in accordance with the quality assurance provisions of the applicable container specification shown in section 5. The inspection of marking for shipment and storage shall be in accordance with MIL-STD-129. The inspection of commercial packaging shall be as specified in the contract (see 6.2).
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