ABSTRACT
A mask is needed to give the diver adequate vision underwater. e mask usually covers the eyes and nose. Traditionally, masks were made from rubber, although now most are made from silicone. e mask seals by pressing on the cheeks, forehead and under the nose with a so silicone edge to prevent entry of water. Swimming goggles, which do not cover the nose, are not suitable for diving. e nose must be enclosed in the mask so that the diver can exhale into it to allow equalization of the pressure between the face and mask with the water environment. It should be possible to block the nostrils without disturbing the mask seal to enable the wearer to perform a Valsalva manoeuvre. Full-face masks that cover the mouth as well as the eyes and nose, or helmets that cover the entire head, are more commonly used by professional divers and are considered in the section on professional diving equipment.
