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MIL-V-27296C

2.3 Order of Precedence. In the event of a conflict between the text of this document and the references cited

herein (except for related associated detail specifications, specification sheets, or MS standards), the text of this

document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless

a specific exemption has been obtained.

3. REQUIREMENTS

3.1 Qualification. The combination inhalation and exhalation oxygen mask valve furnished under this

specification shall be products which are authorized by the qualified activity for listing on the applicable qualified

products list at the time of award of contract (see 4.4 and 6.3).

3.2 Selections of specifications and standards. Specifications and standards for necessary commodities and

services not specified herein shall be selected in accordance with MIL-STD-970.

3.3 Materials. Materials shall be as specified herein. When materials are used which are not specifically

designated they shall be of the best quality and entirely suitable for the purpose intended. Unless otherwise

Specified by the procuring activity, all materials and all component parts used in the valve shall have been

manufactured not more than 12 months prior to the date of delivery Of the valves.

3.3.1 Nonmetallic materials. Any nonmetalic material that is easily deteriorated or otherwise adversely

affected by continued service use with oxygen shall not be used. Whenever diaphragms or flappers are used in the

construction of the type I valve, they shall be made of a silicone rubber. Diaphragms, flappers and the sealing and

isolation washers for the type II valves shall be made of a silicone-type rubber. All silicone-type rubber must be

acceptable to the procuring activity.

3.3.2 Dissimilar metals. Unless suitable protected against electrolytic corrosion dissimilar metals shall not be

used in intimate contact with each other. Dissimilar metals are defined in MIL-STD-889.

3.3.3 Aluminum or aluminum allows. Aluminum or aluminum alloys,when used shall be anodized black in

accordance with MIL-A-8625, type II

3.3.4 Protective treatment. When materials are used in the construction of the valve that are subject to

corrosion in oxygen, salt air, or other atmospheric conditions likely to occur during service usage, they shall be

protected against such corrosion in a manner that will in no way prevent compliance with the performance

requirements of this specification. The use of any protective mating that will crack, chip, or scale with age of

extremes of atmospheric conditions shall be avoided.

3.3.5 Corrosion-resistant. All metals parts shall be of the corrosion-resistant type or suitably treated to resist

corrosion. Brass, bronze, phosphor bronze, 18-8 corrosion-resistant steel, and anodized aluminum alloy are

considered satisfactory corrosion-resistant materials.

3.3.6 Silicone rubber. All silicone rubber used in the valves shall be smooth and free from flash, foreign

materials, imperfections, and objectionable odors.

3.3.7 Toxicity. The material used in the valves shall not contain any chemicals or materials that have toxic

properties as a result of being cleaned with 70-percent isopropyl alcohol solution.

3.4 Desire. The valves shall be as defined by figure 1 and shall conform to the envelope dimensions shown

in figure 2. They shall each consist of a valve body, a cap conforming to figure 3, and bearing and sealing washers

as described for each type valve in figure 4 and 5. The valves shall be designed to control the oxygen pressure

within a mask and to respond automatically to changes in the regulator. The valves shall be mounted in the

expiatory chamber of pressure breathing type masks and shall form a leak tight fit in the exhalation port.

Additionally, care shall be taken in the type I valve design to assure that the exhalation ports on the valve shall not

become blocked by the inner walls of the mask's rubber anti-icing boot. The valves shall embody the design