(c) Blow hard to force air out around the edges of the mask. You
should feel the air escaping around the edges of the mask.
(11) Check your mask for leaks.
(a) Place the palms of your hands over both inlet valve caps. You can
do this with your hands over the hood (figure 1-3D) or under the hood.
(b) Apply pressure with both hands to seal the inlet valves.
(c) Inhale forcibly and hold your breath. If there are no leaks, your
mask will collapse against your face and stay that way until you exhale.
(d) If your mask does not collapse, stop breathing and check to see if
anything (hair, clothing, and so forth) is between your face and the mask. Also check
the head straps and head pad to see if they are twisted. Remove anything between
your mask and face and untwist any twisted straps. Tighten the head straps if needed.
Then clear and check your mask again.
(12) Resume normal breathing.
(13) Pull the hood up and over your head and down onto your shoulders. If
you have not yet put on your protective overgarment, delay step 14 until you have
donned the overgarment.
(14) Zip the front of the hood. Make sure it is closed all the way. Make sure
the edge of the hood does not get caught in the collar of the overgarment.
(15) Pull the draw cord slider snug.
(16) Fasten and adjust the underarm straps. Have another soldier assist you
if possible (buddy-aid).
(17) Replace your headgear (apply helmet cover (figure 1-3E).
c. M40 Field Protective Mask. The M40-series chemical-biological mask
(figure 1-4) is currently being issued to units and will replace the M17-series protective
mask as it becomes available. It will become the standard Army field mask. The M40
mask consists of a silicone rubber face piece with in-turned periphery, binocular eye
lens system, and elastic head harness. Other features include front and side
voicemitters, allowing better communication, drink tube, clear and tinted inserts, and a
filter canister with NATO standard threads. The M40 mask provides respiratory, eye,
and face protection against CB agents, toxins, radioactive fallout particles, and
battlefield contaminants. The canister filter cannot be changed in a contaminated
environment. Instructions for care and maintenance of the M40 mask are found in
TMs 3-4240-280-10-1 and 3-4240-300-20&P.