4. 5. 6. 7. 8. 9. Raise the mask to your outthrust chin and bring the head harness over the back of your head. Center the head harness pad on the back of your head and adjust the bottom straps as necessary for proper fit. Close the outlet valve with the heel of the hand and exhale forcibly to clear the mask of contaminated air. Test  the  mask  for  possible  leakage  by placing your palms over the canisters and inhaling normally until the mask collapses against your face and remains collapsed for approximately 10 seconds. Resume normal breathing. Replace headgear and close the carrier flap. The protective mask outlet valve sometimes sticks closed because saliva or sweat has dried on it. If this occurs, you may loosen the valve by blowing into the valve or by massaging the valve. The valve may be massaged with the valve cover partially removed as shown in figure 6-4. CANISTER REPLACEMENT.  —A pair of replacement canisters for the ND Mk V mask is provided in a hermetically sealed “coffee can” container. While sealed in this container, the canisters have an indefinite shelf life. Therefore, the container seal should not be broken until the canisters are to be mounted on the mask. Once unsealed, the container should not be resealed, and the canisters should be permanently removed from it. The  following  procedures  are  used  for removing  and  replacing  canisters  on  the  ND Mk V mask. To remove each canister from the  facepiece,  you  should  take  the  following actions: 1. Roll approximately one-third of the rubber apron back over the edge of the canister. 2. Slide the canister off the holder. To install new canisters on the facepiece, you should proceed as follows: 1. 2. 3. 4. Remove the canisters from the hermetically sealed container. Roll the rubber apron of each canister completely over the outer edge of the canister. Position each canister snugly against its holder  so  that  the  holder  contacts  the perforated plate of the canister at all points of its outer edge. Roll the rubber apron of each canister over the back of the canister holder. CARE OF THE ND MK V MASK. —Because of  the  importance  of  the  mask,  it  should  be maintained in an efficient operating condition. Careful attention should be given to stowing, cleaning, handling, and inspecting the mask to prolong its useful life. The mask should be stowed in a cool, dry, dark area free from solvents and their vapors. Oil Figure 6-4.-Correcting sticking outlet partially removed. valve with cover and gasoline vapors weaken the rubber and are especially damaging to the activated charcoal in unsealed canisters. The mask must be kept dry. Moisture causes rotting of parts, corroding metal,  deteriorating  canisters,  and  mildewing carriers. The mask should be thoroughly cleaned with soap and water and dried before it is stowed. If the mask was previously used and is to be issued to another person, it should be sterilized with a 6-12