M24BS-OS-02 profession fashion diving mask-scuba free diving equipment

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    Older diving masks had a single elliptical pane of glass. These masks have indentations underneath, either side of the nose. Divers can then put a thumb and forefinger in to pinch the nose, when performing a Valsalva maneuver to clear their ears. This design was improved by bringing the window closer to the face, reducing the volume of air inside the mask, thus making mask clearing easier. The window has a cutout to fit over the nose, which is covered by the rubber or silicone material of the mask. This facilitates pinching the nose when ear-clearing.

    A further development is the mask with two windows, one window for each eye. It can have the windows closer to the face than the one-window type, and therefore contain even less space for the diver to have to blow water out of if the mask floods. These types are often called a "low-volume mask". Participants in the sport ofunderwater hockey are required to use twin-lens masks of this type for their own safety - the sport uses a heavy lead puck similar to an ice hockey puck but skilful players can give the puck considerable height when making passes which leads to the possibility of accidental puck contact with other players. Should a puck hit the lens of a single-lens mask there is a good chance it will break the glass and pass through the aperture into the face and eyes, but with a twin-lens mask though the glass may still break the frame will prevent the passage of the puck any further.

   M24BS-OS-02 profession fashion diving mask-scuba free diving equipment

M24BS-OS-02 profession fashion diving mask-scuba free diving equipment

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