Modern masks are probably one of the most unique styles and personalized equipment you find in a diving center. However, although they look different, all masks (even the old porthole-style \"frogman \" masks seen in 1950s films) do three basic things:
1. The mask adds a gap between the eyes and the water.Not only is this more comfortable; it is necessary on the body for your eyes to see and focus properly. Your eyes are naturally focused in the air, so without the airspace in front of you, things underwater will look blurry. The airspace provided by the mask restores sharpness (if you normally wear glasses, many diving masks can use prescription lenses).
2. The mask provides a pocket where you can pinch your nose with your fingers.Why do you want to do this? Because the easiest way to balance (or\"clear\" your ears) is to be able to squeeze your nostrils closed and fill the airspace of your ears by gently blowing towards the closed nostrils. This pushes air from your lungs into the air space of your ears, just as you balance your ears at high altitudes or when flying. After diving for a while, you may be good at cleaning your ears without even touching your nose. But during the first few dives of the season, or if you're even a little crowded, you want to be able to close your nose and need a flexible nose bag for you to do so. Therefore, choose a mask design that can easily pinch your nose.
3. The mask provides a way to equalize pressure and drain collected water.Many non-divers believe that the reason masks surround the nose and eyes is to prevent water from flowing out of the nose and do not require a nose clip. Mask design can certainly do this, but that's not the real reason for the nose contained in your mask-it's just a handy side effect. The real reason for having a mask covering your nose is that you can exhale into the mask space through the nose, adding air to balance the air pressure inside the mask to match the hydrostatic pressure of the water pushing the mask from the outside. If you can't do this, the mask will quickly develop\"squeezing\" and become uncomfortable as you go deeper. Also, if water enters and accumulates at the bottom of the mask, you will want to be able to remove it easily. With most masks, you simply breathe through your nose while tilting the mask slightly, so water is squeezed out of the flexible skirt at the bottom of the mask. Some masks have a one-way cleaning valve at the bottom of the mask; with these you don't even need to touch the mask to clear it. All you need to do is tilt your head so that the wash is at the lowest point of the mask, exhale through your nose and all the water is drained from the wash valve.
All diving masks today are likely to do their main job-let you see, keep you balanced, and clean up easily. But unless it fits your face, no mask can do any of the three. Different brands and types of masks are more suitable for different face types. Your retail diving professional will experience which masks are good for things like narrow faces and which are best for people with protruding cheekbones or wider faces. In addition, some manufacturers offer the same basic mask models in different sizes to better fit individual faces.
The long-established method for checking the fit of a mask is to fix it on the face without using a strap. Simply inhale the nose, create low pressure in the mask, and then hold your breath to see if a mask will Close to your face. A mask that comes off immediately, or a mask that falls off within a few seconds, is a mask that leaks air on one of its edges. If the mask leaks, it also leaks water.
Once you find a variety of masks that can stay on your face, you can do a variety of other tests to see if your mask and face will form the perfect match. One is to gently apply the mask to your face and exhale through your nose. If the air leaves the mask in only one or two places, the mask seal may not be strong enough for your particular face. However, if the soft edges of the mask skirt flutter more or less evenly, then this is another sign that you are finding a good match.
However, the most important test is to have a knowledgeable person, such as a staff member at a local diving center, carefully check the way the mask is worn on the face. Not only will he or she look for a good seal; a knowledgeable professional will look for other nuances as well:
Is the eye naturally centered in the lens area? Does the skirt pass through the hairline or eyebrows, causing a potential leak?
If you are a man with a moustache, does this special mask skirt have enough sealing area on your beard to prevent you from being bothered by penetration?
Will this type of mask complement your main dive?