a. Stop Breathing. Stop breathing (hold your breath without inhaling) and close
b. Remove Helmet. Remove your helmet. If you have a M42-series mask,
place the helmet in a convenient location that is not contaminated. If you have a M17-
series, M24-series, M40-series, M43-series, or M-45 series mask, put your helmet
between your thighs or hold your rifle between your thighs and place your helmet on the
c. Take Off Glasses. Take off your glasses if you are wearing them and store
them in a safe location.
d. Obtain the Mask. Open your mask carrier with one hand. Grasp the mask
assembly with your other hand and remove the mask from the carrier.
e. Don the Mask.
(1) Put your chin in the chin pocket of the mask and press the facepiece
snugly against your face.
(2) Grasp the tab and pull the head harness over your head. Make sure
your ears are between the temple straps and the cheek straps. Make sure the head
harness is pulled far enough over so the forehead straps are tight. (The temple and
forehead straps should have been properly adjusted before starting the mission.)
(3) Use one hand to tighten the cheek straps one at a time while holding the
head pad centered on the back of your head with the other hand. Make sure the straps
lay flat against your head.
f. Clear the Mask.
(1) Seal the outlet valve by pushing in the center of the outlet valve cover
with one hand
(2) Blow hard to force air out around the edges of the mask. You should
feel the air escaping around the edges of the mask. This forces contaminated air from
g. Check the Mask for Leaks.
(1) Cover the inlet port of the filter canister (M40-series and M-45-series) or
the inlet port of the armor quick disconnect (M42-series) with the palm of your hand and
(2) If the facepiece collapses against your face and remains collapsed while
you hold your breath, the mask is airtight.