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A scuba set, originally just scuba, is any breathing apparatus that is entirely carried by an underwater diver and provides the diver with breathing gas at the ambient pressure. Scuba is an anacronym for self-contained underwater breathing apparatus. Although strictly speaking the scuba set is only the diving equipment that is required for providing breathing gas to the diver, general usage includes the harness or rigging by which it is carried and those accessories which are integral parts of the harness and breathing apparatus assembly, such as a jacket or wing style buoyancy compensator and instruments mounted in a combined housing with the pressure gauge. In the looser sense, scuba set has been used to refer to all the diving equipment used by the scuba diver, though this would more commonly and accurately be termed scuba equipment or scuba gear. Scuba is overwhelmingly the most common underwater breathing system used by recreational divers and is also used in professional diving when it provides advantages, usually of mobility and range, over surface-supplied diving systems and is allowed by the relevant legislation and code of practice.
Aqua-Lung was the first open-circuit, self-contained underwater breathing apparatus to achieve worldwide popularity and commercial success. This class of equipment is now commonly referred to as a twin-hose diving regulator, or demand valve. The Aqua-Lung was invented in France during the winter of 1942–1943 by two Frenchmen: engineer Émile Gagnan and Jacques Cousteau, who was a Naval Lieutenant. It allowed Cousteau and Gagnan to film and explore underwater more easily.
Ice diving is a type of penetration diving where the dive takes place under ice. Because diving under ice places the diver in an overhead environment typically with only a single entry/exit point, it requires special procedures and equipment. Ice diving is done for purposes of recreation, scientific research, public safety and other professional or commercial reasons.
A diving regulator or underwater diving regulator is a pressure regulator that controls the pressure of breathing gas for underwater diving. The most commonly recognised application is to reduce pressurized breathing gas to ambient pressure and deliver it to the diver, but there are also other types of gas pressure regulator used for diving applications. The gas may be air or one of a variety of specially blended breathing gases. The gas may be supplied from a scuba cylinder carried by the diver, in which case it is called a scuba regulator, or via a hose from a compressor or high-pressure storage cylinders at the surface in surface-supplied diving. A gas pressure regulator has one or more valves in series which reduce pressure from the source, and use the downstream pressure as feedback to control the delivered pressure, or the upstream pressure as feedback to prevent excessive flow rates, lowering the pressure at each stage.
Surface-supplied diving is a mode of underwater diving using equipment supplied with breathing gas through a diver's umbilical from the surface, either from the shore or from a diving support vessel, sometimes indirectly via a diving bell. This is different from scuba diving, where the diver's breathing equipment is completely self-contained and there is no essential link to the surface. The primary advantages of conventional surface supplied diving are lower risk of drowning and considerably larger breathing gas supply than scuba, allowing longer working periods and safer decompression. Disadvantages are the absolute limitation on diver mobility imposed by the length of the umbilical, encumbrance by the umbilical, and high logistical and equipment costs compared with scuba. The disadvantages restrict use of this mode of diving to applications where the diver operates within a small area, which is common in commercial diving work.
A diving helmet is a rigid head enclosure with a breathing gas supply used in underwater diving. They are worn mainly by professional divers engaged in surface-supplied diving, though some models can be used with scuba equipment. The upper part of the helmet, known colloquially as the hat or bonnet, may be sealed directly to the diver using a neck dam, connected to a diving suit by a lower part, known as a breastplate, or corselet, depending on regional language preferences, or simply rest on the diver's shoulders, with an open bottom, for shallow water use.
A full-face diving mask is a type of diving mask that seals the whole of the diver's face from the water and contains a mouthpiece, demand valve or constant flow gas supply that provides the diver with breathing gas. The full face mask has several functions: it lets the diver see clearly underwater, it provides the diver's face with some protection from cold and polluted water and from stings, such as from jellyfish or coral. It increases breathing security and provides a space for equipment that lets the diver communicate with the surface support team.
A diving air compressor is a breathing air compressor that can provide breathing air directly to a surface-supplied diver, or fill diving cylinders with high-pressure air pure enough to be used as a hyperbaric breathing gas. A low pressure diving air compressor usually has a delivery pressure of up to 30 bar, which is regulated to suit the depth of the dive. A high pressure diving compressor has a delivery pressure which is usually over 150 bar, and is commonly between 200 and 300 bar. The pressure is limited by an overpressure valve which may be adjustable.
A breathing apparatus or breathing set is equipment which allows a person to breathe in a hostile environment where breathing would otherwise be impossible, difficult, harmful, or hazardous, or assists a person to breathe. A respirator, medical ventilator, or resuscitator may also be considered to be breathing apparatus. Equipment that supplies or recycles breathing gas other than ambient air in a space used by several people is usually referred to as being part of a life-support system, and a life-support system for one person may include breathing apparatus, when the breathing gas is specifically supplied to the user rather than to the enclosure in which the user is the occupant.
Buddy breathing is a rescue technique used in scuba diving "out-of-gas" emergencies, when two divers share one demand valve, alternately breathing from it. Techniques have been developed for buddy breathing from both twin-hose and single hose regulators, but to a large extent it has been superseded by safer and more reliable techniques using additional equipment, such as the use of a bailout cylinder or breathing through a secondary demand valve on the rescuer's regulator.
A scuba manifold is a device incorporating one or more valves and one or more gas outlets with scuba regulator connections, used to connect two or more diving cylinders containing breathing gas, providing a greater amount of gas for longer dive times or deeper dives. An isolation manifold allows the connection between the cylinders to be closed in the case of a leak from one of the cylinders or its valve or regulator, conserving the gas in the other cylinder. Diving with two or more cylinders is often associated with technical diving. Almost all manifold assemblies include one cylinder valve for each cylinder, and the overwhelming majority are for two cylinders.
In underwater diving, an alternative air source, or more generally alternative breathing gas source, is a secondary supply of air or other breathing gas for use by the diver in an emergency. Examples include an auxiliary demand valve, a pony bottle and bailout bottle.
Scuba gas management is the aspect of scuba diving which includes the gas planning, blending, filling, analysing, marking, storage, and transportation of gas cylinders for a dive, the monitoring and switching of breathing gases during a dive, efficient and correct use of the gas, and the provision of emergency gas to another member of the dive team. The primary aim is to ensure that everyone has enough to breathe of a gas suitable for the current depth at all times, and is aware of the gas mixture in use and its effect on decompression obligations, nitrogen narcosis, and oxygen toxicity risk. Some of these functions may be delegated to others, such as the filling of cylinders, or transportation to the dive site, but others are the direct responsibility of the diver using the gas.
Scuba skills are skills required to dive safely using self-contained underwater breathing apparatus, known as a scuba set. Most of these skills are relevant to both open-circuit scuba and rebreather scuba, and many also apply to surface-supplied diving. Some scuba skills, which are critical to divers' safety, may require more practice than standard recreational training provides to achieve reliable competence.
Surface-supplied diving equipment (SSDE) is the equipment required for surface-supplied diving. The essential aspect of surface-supplied diving is that breathing gas is supplied from the surface, either from a specialised diving compressor, high-pressure gas storage cylinders, or both. In commercial and military surface-supplied diving, a backup source of surface-supplied breathing gas should always be present in case the primary supply fails. The diver may also wear a bailout cylinder which can provide self-contained breathing gas in an emergency. Thus, the surface-supplied diver is less likely to have an "out-of-air" emergency than a scuba diver using a single gas supply, as there are normally two alternative breathing gas sources available. Surface-supplied diving equipment usually includes communication capability with the surface, which improves the safety and efficiency of the working diver.
Diving hazards are the agents or situations that pose a threat to the underwater diver or their equipment. Divers operate in an environment for which the human body is not well suited. They face special physical and health risks when they go underwater or use high pressure breathing gas. The consequences of diving incidents range from merely annoying to rapidly fatal, and the result often depends on the equipment, skill, response and fitness of the diver and diving team. The classes of hazards include the aquatic environment, the use of breathing equipment in an underwater environment, exposure to a pressurised environment and pressure changes, particularly pressure changes during descent and ascent, and breathing gases at high ambient pressure. Diving equipment other than breathing apparatus is usually reliable, but has been known to fail, and loss of buoyancy control or thermal protection can be a major burden which may lead to more serious problems. There are also hazards of the specific diving environment, and hazards related to access to and egress from the water, which vary from place to place, and may also vary with time. Hazards inherent in the diver include pre-existing physiological and psychological conditions and the personal behaviour and competence of the individual. For those pursuing other activities while diving, there are additional hazards of task loading, of the dive task and of special equipment associated with the task.
A built-in breathing system is a source of breathing gas installed in a confined space where an alternative to the ambient gas may be required for medical treatment, emergency use, or to minimise a hazard. They are found in diving chambers, hyperbaric treatment chambers, and submarines.
Diving procedures are standardised methods of doing things that are commonly useful while diving that are known to work effectively and acceptably safely. Due to the inherent risks of the environment and the necessity to operate the equipment correctly, both under normal conditions and during incidents where failure to respond appropriately and quickly can have fatal consequences, a set of standard procedures are used in preparation of the equipment, preparation to dive, during the dive if all goes according to plan, after the dive, and in the event of a reasonably foreseeable contingency. Standard procedures are not necessarily the only courses of action that produce a satisfactory outcome, but they are generally those procedures that experiment and experience show to work well and reliably in response to given circumstances. All formal diver training is based on the learning of standard skills and procedures, and in many cases the over-learning of the skills until the procedures can be performed without hesitation even when distracting circumstances exist. Where reasonably practicable, checklists may be used to ensure that preparatory and maintenance procedures are carried out in the correct sequence and that no steps are inadvertently omitted.
The mechanism of diving regulators is the arrangement of components and function of gas pressure regulators used in the systems which supply breathing gases for underwater diving. Both free-flow and demand regulators use mechanical feedback of the downstream pressure to control the opening of a valve which controls gas flow from the upstream, high-pressure side, to the downstream, low-pressure side of each stage. Flow capacity must be sufficient to allow the downstream pressure to be maintained at maximum demand, and sensitivity must be appropriate to deliver maximum required flow rate with a small variation in downstream pressure, and for a large variation in supply pressure, without instability of flow. Open circuit scuba regulators must also deliver against a variable ambient pressure. They must be robust and reliable, as they are life-support equipment which must function in the relatively hostile seawater environment, and the human interface must be comfortable over periods of several hours.
Human factors in diving equipment design are the influences of the interactions between the user and equipment in the design of diving equipment and diving support equipment. The underwater diver relies on various items of diving and support equipment to stay alive, healthy and reasonably comfortable and to perform planned tasks during a dive.
References
- ↑ Brittain, Colin (2004). "Practical diver training". Let's Dive: Sub-Aqua Association Club Diver Manual (2nd ed.). Wigan, UK: Dive Print. p. 48. ISBN 0-9532904-3-3 . Retrieved 6 January 2010.[ permanent dead link ]
