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|  MIL-M-19417D
3.3 Matertals. Materials shall conform to applicable specifications
and shall be as specified herein and on applicable drawings. Materials which
are not covered by specifications, or which are not specifically described
herein, shall be of the best quality, of the lightest practicable weight, and
suitable for the purpose intended.
3.3.1 Nonmetallic materials. Any nonmetallic material that is
adversely affected by continued use with oxygen shall not be used.
3.3.2 Age. Elastomer components, except silicone, shall not be more
than 12 months old from the date of manufacture to the date of delivery to any
Government service or to any airframe or accessory manufacturer.
3.3.3 Elastomer components. The elastomer components shall be composed
of an ozone resistant composition, which shall not bloom, and shall meet the
requirements for ozone resistance (see 3.6.11) when tested in 4.7.10.2 and
4.7.11.
3.3.4 Protective treatment. When materials are used in the
construction of the masks assemblies that are subject to deterioration when
exposed to environmental conditions likely to occur during service usage, they
shall be protected against such deterioration in a manner that will in no way
prevent compliance with the performance requirements of this specification.
Protective coatings which might crack, chip or scale during normal service life
or under extremes of environmental conditions shall not be used.
3.4 Standard parts. MS and AN standard parts shall be used where they
suit the purpose. They shall be Identified on the manufacturer's drawings by
their part numbers. Parts which are not covered by specifications or military
standards, or which are not specifically described herein or on the drawings,
shall be completely described on manufacturer's drawings.
3.5 Design and construction. The design and construction of the mask
assemblies shall be in accordance with the applicable documents specified in the
contract or order (see 6.2b). The mask assembly shall be constructed to permit
use of the mask assembly with either a headset (earphones) or a protective
helmet without degradation of protection.
3.5.1 Mask.
3.5.1.1 Lens. The lens shall be of one piece construction and shall be -
fabricated of an allyl based resin conforming to the physical properties
specified in 4.7.10.1. Provisions shall be made for replacement of the lens
when required. The mask shall contain provisions for the non-fogging of the
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lens at an ambient temperature of 50 F and the design of the lens shall be such
as to provide for maximum visibility. The optical uniformity of the lens shall
conform to the requirements specified in MIL-P-5425.
3.5.1.2 Microphone support. The mask shall contain adequate provisions
for the installation of the AM-4326B/A dynamic microphone amplifier conforming
to MIL-A-23595/2 and a dynamic microphone conforming to MIL-M-26542/6 or
MIL-M-26542/7, as specified by the acquiring activity (see 6.2e). The in-line
amplifier for the dynamic microphone shall be placed outside the mask. The
location of the support (microphone housing) shall be centrally located such as
to provide for maximum fidelity of voice transmittal signals. The Installation
of either microphone in this support shall not interfere with normal operation
of either the inlet or outlet valves, or with the facial fit of the mask.
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