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Some soldiers have heads that are bigger or smaller than average, which makes finding a mask that fits them difficult. These fitting solutions may solve your fitting problems, NBC NCOs:

Use the M41 protection assessment test system (PATS) instead of banana oil to test every mask. PATS is much more accurate than banana oil. A mask that flunks with banana oil may pass with a more accurate test. If a small mask is too big to create a good seal, readjust and tighten the head harness, then test with PATS again. Sometimes that's enough for the mask to pass.

If the mask still doesn't pass, replace the head harness with a skull cap head harness, NSN 4240-01-390-3057, and re-check.

Still no luck? Then check out TB 3-4240-341-20-1, Chemical-Biological Protective Mask for Hard-to-Fit Service Members, for further help. If nothing works, tell your CO. He will decide if the soldier is deployable. Sometimes the M45 land warrior mask will fit when other masks don't.

Check out the TB if the M40 or M42 large mask is too small for a soldier, too.