Figure 6-2.-The ND Mk Vsensory effects, such as a continuous flow of tears,might indicate that replacement is needed.Two types of protective masks have been ingeneral use in the Navy: the M17A1, issued toshore-based personnel, and the ND Mark (Mk)V, issued to forces afloat. Both of these, however,are being phased out and replaced by theMCU-2/P mask. All masks consist of a facepieceand filter system. The facepiece provides agastight seal around the face, protecting the eyes,lungs, and facial skin. The filter system is attachedto the facepiece; it filters out or absorbs airborneradioactive material and BW/CW agents beforeair enters the facepiece for inhalation. The mainpurpose of the mask is to purify the air beingbreathed by its wearer. To effectively purify theair, the mask must meet two requirements. First,the facepiece must fit snugly over the face toprovide a perfect seal. Second, the filter systemmust prevent any contaminated material orchemical agent from entering the mask.ND Mk V Protective MaskA unique design feature of the ND Mk Vprotective mask makes it ideally suited forshipboard use. A pneumatic cushion locatedaround the underside edge of the facepiece allowsthe facepiece to conform to the wearer’s face;therefore, an airtight seal is possible for virtuallyall facial shapes. This feature permits the issueprotective mask.of the mask in only one size and, thus, eliminatesthe need for stowing and issuing various sizes ofprotective masks aboard ship.The major components of the ND Mk V pro-tective mask are shown in figure 6-2. The maskfacepiece is made of a black, flexible rubbercompound formulated to retard the penetrationof chemical agents. The wide-vision eyepiece isa clear, flexible, one-piece plastic lens curved tothe shape of the facepiece. Voice transmission ispermitted by a thin plastic membrane in thediaphragm assembly. Other features of thefacepiece include the air-inlet and exhaust valvesand the canister holders. Air deflectors, locatedinside the mask, create a flow of air from theair-inlet valves across the eyepiece to reducefogging.Filtration for the mask is provided by filtercanisters mounted on the two canister holders onthe facepiece. Each of these filter canisterscontains a treated paper filter and an activatedcharcoal filter. The treated paper filter removesparticulate matter, and the activated charcoalfilter absorbs toxic vapors and aerosols from theinhaled air. A rubber apron affixed to eachcanister attaches the canister to the holder on thefacepiece. The rubber apron provides an airtightseal around this connection when it is rolled overthe back of the canister holder.6-10
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