The Encyclopedia & Guide to Diving with a Full Face Mask

Features of Full Face Masks Full face masks have different features dependent upon the manufacturer and model. Not all full face masks have the features described in this guide. Generally, divers may find that full face masks have many of these features or may have one feature in lieu of another. Full face masks have large face/view ports which are the lenses of the mask. These lenses are not custom made for eye prescriptions. Full face masks can accept custom eye prescription inserts which mount inside the mask at the face port. Manufacturers should be consulted on models which have the capability to house prescription eye wear. The full face mask has a mask skirt which seals against the diver’s skin or to a hood to prevent water from entering the mask, just as traditional half masks have. Some masks, such as the OTS Guardian full face mask, have a double skirt, which may provide a better seal than a single skirt. The skirt of a full face mask is often wider than that of traditional half mask and therefore can afford a better water tight seal. Weights are sometimes added to the full face mask to balance it underwater or to counter any buoyancy characteristics that have a negative impact on the diver due to the larger volume of breathing gas contained in the mask as compared to a traditional half mask. The regulator is similar to that of a traditional second stage. However, it is affixed to the full face mask rather than a mouth piece. Most regulators in full face masks are demand regulators, meaning the regulator delivers breathing gas, at or above ambient pressure, only when the diver begins to inhale and then stops delivering breathing gas as the diver is exhaling. Some full face masks are free-flow which means the regulator is constantly delivering breathing gas regardless of the diver’s inhaling or exhaling. This is not efficient for scuba as it requires a large breathing supply which is not realistic with the utilization of a scuba tank. With surface supplied diving, using low pressure compressors as a gas supply, free-flow masks are widely used in commercial diving. The rubber pocket which contains the diver’s nose and mouth inside the full face mask is the oral-nasal/orinasal pocket. The oral-nasal provides a confined space for the diver to exhale immediately into the exhaust of the mask. This is essential to prevent exhaled carbon dioxide (CO2) from building in the large volume space that makes up the entire interior of the mask. Carbon dioxide build-up can render a diver unconscious and contributes to diver ailments which include hypothermia and decompression sickness . The oral-nasal is a necessary component for most all full face masks, if being used with scuba, to prevent the carbon dioxide problems associated with diving. This is because scuba works on demand. Free flow masks will flush the CO2 out of the mask. Some full face masks utilize a mouth piece which negates the necessity of the oral-nasal.