Diving mask
The diving mask (also called diving mask or pressure equalization mask ) is part of diving equipment and belongs to the basic equipment (ABC equipment) of a diver . It consists of a body made of soft rubber or silicone , in which a flat lens is inserted at the front and which has soft sealing lips towards the diver's face, which prevent water from penetrating the diving mask. The sealing lips are mostly made of silicone, as this does not trigger any allergic reactions when it comes into contact with the skin. An adjustable elastic band holds the diving mask on the head.
In the vernacular , the diving mask is also called diving glasses or goggles called. These terms do not make sense because, unlike glasses, a mask also encloses the nose.
The diving mask is to be distinguished from swimming goggles in particular . The swimming goggles protect the eyes from chlorinated water, for example. It differs from the diving mask in that it has smaller glasses and the lack of a nasal cavity, as well as the simpler straps.
construction
A diving mask is equipped with:
- a tempered glass window . Expensive panes of laminated glass (glass and plastic bonded in layers) are largely unbreakable. Plexiglass panes are break-proof, but they scratch easily.
- a nasal cavity through which the diver can hold his nose to equalize pressure while diving (or blow air into it to prevent negative pressure ) without removing the mask .
- a double sealing edge
- a headband, mostly made of silicone or neoprene in two parts.
function
Nose notch for pressure compensation
A diving mask is exposed to increasing pressure while diving, which has to be compensated regularly. For this purpose, a diving mask can be filled with additional air at any time by blowing air from the nose into the nasal cavity under water. This prevents excessive pressure on the mask when descending. A pressure equalization takes place inside the mask. If the pressure in the mask is not equalized during the dive , this can lead to barotraumas in the form of pressure points on the face to ruptured blood vessels on the eyeball or even a detachment of the retina .
When you emerge, the air inside the mask expands again and escapes through the nose or the mask's sealing lip. Masks are also available that have a valve at the tip of the nasal orifice through which air can escape.
The nasal cavity in half-face masks is made of flexible material so that the nose can be compressed with the hand and the pressure equalization in the middle ear can be completed. Some full face masks provide for the nose to be closed "from below". The pressure equalization of the middle ear is independent of the pressure equalization of the interior of the mask and can also be done without a mask.
See underwater
The human eye and its dioptric apparatus are adapted to the optical density of air . If the eye comes into direct contact with water , whose refractive index is very close to that of the cornea , the rays are only slightly refracted and no longer meet in the focal point on the retina - the diver sees blurred. Since with a diving mask the light rays do not hit the cornea directly from the water, but from the air space within the mask, this enables the diver to have a visual acuity under water that corresponds to that on land.
Children - whose pupils and lenses adapt better to the circumstances - can see clearly underwater and without aids, especially after training. This was shown in a study carried out on eight- to thirteen-year-old Moken children as well as European children.
The refractive index at the transition between mask and water is 1.33 (4/3) and causes an increase in the air space in front of the eyes : objects appear 33% larger and distances 25% smaller than they really are. For example, a three meter long object appears to be four meters long (magnification 33%) and a four meter distance to the object appears only three meters (25% closer).
Diving masks for ametropia
Wearers of glasses can use a diving mask with optically polished inserts or they can wear contact lenses under an ordinary diving mask. The outer surface of the mask glasses are flat in both cases. The refractive power of the diving mask can be set positively or negatively via the curvature of the inner surface, depending on which ametropia needs to be corrected. The interior of the mask is filled with gas both on land and during the dive, so that the diving mask enables sharp vision in both cases. The refractive power of the water behind a flat pane makes objects appear larger, but does not correct ametropia. In the case of minor ametropia, this is "only" a matter of comfort, while ametropia from 1.5 dioptres are considered safety-relevant and therefore in need of correction. Good visibility is important not only under water, but especially on the surface of the water, especially when it comes to emergency ascents in open water at a greater distance from the boat / shore.
condensation
So that the glasses of the mask do not fog up with condensation water due to the large temperature difference between the surrounding water and the interior of the mask , synthetic anti-fogging agents or saliva are sometimes used.
Apnea diving
The equalization of the internal pressure in the mask, which is necessary several times during the dive, is only possible to a limited extent for apnea divers , as they only carry one lung filling of air with them and the repeated pressure equalization in the mask leads to a significant loss of air and thus to shorter dives. Since the air pressure in the lungs corresponds to the water pressure in the environment, the lung volume decreases with increasing depth. However, the volume in the mask remains constant, so that the amount of gas required for pressure equalization increases with depth in relation to the lung volume. In order to reduce the mask volume, many apnea divers inject their mask completely with a filling material such as silicone except for a small viewing channel. This significantly reduces the volume of air to be compensated.
An alternative solution to the mask are special contact lenses.
to form
There are different forms of diving masks:
- Regular masks have a central sight glass.
- Diving masks for apnea diving or underwater rugby have a small inner volume. This means that the diver needs less air for pressure equalization .
- Diving masks with a two-part lens: The often smaller eye relief ensures a large field of vision, the smaller internal volume and the sometimes better fit are perceived as pleasant. They are (also) suitable for inserting optical glasses for people who wear glasses. Today optical lenses are also glued to the inside of the mask.
- Panoramic diving masks have additional windows on the sides and thus offer the diver an extended field of vision. They are also often used in underwater photography to better recognize the face of the person being photographed.
- Full face masks are mainly used by professional divers and when diving in cold or polluted waters. Because the regulator is attached directly to the mask, voice communication is also possible when diving. The masks often have special devices to equalize pressure through the nose. Other precautions, such as inner masks or purge air, largely prevent the lens from fogging up.
- Diving helmets are a special form of diving masks. Compared to full face masks, it is noticeable that there is no possibility of direct pressure equalization via the nose (or only with a nose clip). Similar to full face masks, they offer more protection, apart from plexiglass ball helmets. Light helmets are worn with a neck collar, traditional helmets with a shoulder piece.
- In 1988, Eric Fattah invented a flexible mask called Fluid Goggles that injected a saline solution into the space between the mask and the eye. It also has a lens to allow a clear view. Pressure equalization is therefore no longer necessary. The Trygons company has also been producing a flexible mask called Fluid Goggles since 2007 , which also has no air space between the eye and the water.
Choosing the right diving mask
The tightness and thus the optimal fit of the mask can be checked as follows: If you put the mask on your face and breathe in easily through your nose, the mask should hold on your face. The mask strap should not be too tight or too tight, otherwise the mask body could warp. The mask must fit comfortably and securely. Since every mask is different in its fit and construction, such a simple and quick test cannot be dispensed with. Women in particular should take this test, as they usually have a narrower face.
Especially when scuba diving and deep diving, it is necessary to create a pressure equalization under water between the water pressure and the pressure inside the mask. This is ensured through breathing and the connection through the nasal cavity and through the nose to the pharynx. The nasal cavity should therefore also be accessible with thick neoprene gloves and allow the nostrils to be pinched together. By exhaling through your nose it is also easier to blow out a diving mask filled with water. Since only one lung filling is available per dive during apnea diving, an attempt is made here to reduce the mask volume. When scuba diving, a low mask volume is of no advantage, as the diver always inhales and exhales.
Individual evidence
- ↑ a b c Diving theory: ABC equipment - masks. Archived from the original on December 17, 2013 ; Retrieved May 19, 2011 .
- ↑ a b divers mask , PADI, accessed June 13, 2012.
- ↑ Leaflet M3-001-06: Swimming and diving with swimming goggles. (PDF; 73 kB) DLRG , accessed on May 23, 2013 .
- ↑ Anna Gislén et al .: Superior Underwater vision in a human population of Sea Gypsies . In: Current Biology . tape 13 , no. 10 , May 13, 2003, doi : 10.1016 / s0960-9822 (03) 00290-2 , PMID 12747831 (English).
- ↑ Seeing underwater. Retrieved May 19, 2011 .
- ↑ a b Christoph Klingmann, Kay Tetzlaff: Modern diving medicine: manual for diving instructors, divers and doctors. 2., completely revised Edition. Gentner, Stuttgart 2012, ISBN 978-3-87247-744-6 .
- ↑ Buying tip diving mask - structure and variations. Archived from the original on November 19, 2013 ; Retrieved May 19, 2011 .
- ↑ Liquivision: Fluid Goggles. Retrieved January 25, 2017 (English).
- ↑ Trygon's Designs: Fluid Goggles. Retrieved January 25, 2017 (English).
See also
- Sea-U , contact lens for freedivers
- Visibility under water
