Underwater diving emergency
A diving emergency or underwater diving emergency is an emergency that involves an underwater diver. The nature of an emergency requires action to be taken to prevent or avoid death, injury, or serious damage to property or the environment. In the case of diving emergencies, the risk is generally of death or injury to the diver, while diving or in the water before or after diving.
Underwater diving is an activity in which there is a constant risk of an emergency developing. This is a situation common to many human activities. The diver survives in an inherently hostile environment by competence, suitable equipment, vigilance, and attention to detail at a level appropriate to the specific situation. The emergency is the stage of an accident or incident between the causes and the effects, often while it is still possible to take effective action to rectify or mitigate the situation. Like many other classes of emergency, diving emergencies can often be prevented from developing further by appropriate action at an early stage, and by having the appropriate skills and equipment. Professional diving teams are required to have emergency plans in place during all operations, and recreational divers are also expected to do so, to the extent appropriate to the dive plan.
An alternative meaning, in the context of medicine, is a medical emergency which was initiated while diving, which may also be described as a diving medical emergency.
Scope and definition
A diving emergency is an emergency experienced by a diver during a dive. This includes the time from when the diver enters the water to dive, until the end of all decompression and the diver has exited the water. Surface decompression may legally be part of a dive. It includes but is not restricted to medical emergencies that are a consequence of diving incidents.- An emergency is an unexpected and often unforeseen set of circumstances or the consequences thereof that require immediate action, or an urgent requirement for assistance or relief.
- The human activity of underwater diving is the practice of descending below the water's surface to interact with the environment. It is also often referred to as diving, an ambiguous term with several possible meanings, depending on context.
- Diving emergencies can be grouped as incidents that can be managed by the diver without assistance, and those which require assistance by another diver, the dive team or an outside party.
- Diving emergencies can also be distinguished by the mode of diving, so a distinction can be made between scuba diving emergencies and freediving emergencies, surface-oriented surface-supplied diving emergencies and saturation diving emergencies, and open circuit and rebreather emergencies, as some emergencies are only possible when diving in a specific mode, and for others the risk is strongly influenced by the mode.
Types and causes
Types
- Life support emergencies
- Decompression emergencies
- Incapacitation
- Acute medical conditions
Causes
- Medical emergencies can be the consequence of an emergency with another cause, a health problem, or mismanagement of a routine situation or minor contingency.
- Equipment failures that constitute an emergency are usually failures of life-support equipment, but also can be failures of other equipment that make it difficult, dangerous, or impossible to properly operate safety critical equipment, or to reach a place of safety, such as dive computer lockout or failure with decompression obligation, catastrophic dry-suit flooding, catastrophic loss of buoyancy, loss of insulation in very cold conditions, regulator freeze with free-flow, dislodging of the regulator or full-face mask, helmet comes off the head, roll-off of cylinder valve, or a burst breathing gas hose. Some of these can also be caused by diver or team error.
- Diver errors. such as running out of gas, overstaying at depth and developing a decompression obligation beyond the remaining gas endurance, Losing the guideline under an overhead. Equipment failure due to improper preparation and checks. Inappropriate response to an adverse event, such as panic, can cause a routinely recoverable situation to deteriorate into an emergency.
- Team errors. emergencies which are the consequences of a person or group involved in the dive, including contracted service providers. eg: Divers left behind at sea, or run over by the dive boat.
- Third party influences. For example dynamic positioning runout, a diver being hit by a passing boat, or an umbilical pulled into a thruster.
- Environmental problems, situations, effects, or influences such as unforecast weather deterioration, stronger current than anticipated, unexpected low water temperature, silt-out, inadvertent entry into a confined space or overhead environment in low visibility without a guideline to open water, entrapment by nets, lines, wreckage, delta-p situations, collapse of structure, wreckage or overhead, Marine animal injuries, contamination by hazardous materials, surf and currents too strong or mismanaged. Inability to get to exit point due to wind, waves, or currents. Conditions at planned or contingency exit point too rough to exit. Divers carried away from the intended exit area or across a shipping lane by currents.
Life support emergencies
Out-of-gas incidents
An out-of-gas emergency is a life-support emergency which occurs when the breathing gas supply is cut off by running out, supply system failure, or supply system interruption. These are the most urgent of the common diving emergencies, and the ones the diver should be equipped and skilled to manage. Many out-of-air emergencies are consequences of other problems that were not effectively managed.A similar emergency occurs when a scuba diver accumulates more decompression obligation than the available gas endurance for decompression. This can happen either by the diver being unable to ascend in time to avoid the problem, or by using up or losing gas supply due to circumstances or inattention. This form of out-of-gas incident develops with the knowledge of the diver, who has more time available to work on a solution if one exists. It is analogous to the problem of being unable to ascent from under an overhead obstruction, and the decompression obligation is sometimes referred to as a decompression overhead.
Contaminated scuba gas supply
This is usually a consequence of poor filling procedures and often a problem of contaminated intake air. Bailout to another gas source is the preferred option, but it may be necessary to surface on the gas in use. Consequences depend on the specific contaminant and exposure. Carbon monoxide, carbon dioxide, volatile hydrocarbons, and compressor lubricant are the most commonly encountered contaminants, and there may be legislation requiring compressors used in this service to be periodically tested for these contaminants. It is possible though unlikely for mixed breathing gas blended using high pressure industrial grade oxygen that is not certified for breathing grade, to contain contaminants not permitted in a breathing gas.Contaminated surface gas supply
It is possible for the surface gas supply to be contaminated, so there will be an alternative surface supply to the gas distribution panel, which can be switched over with minimal delay, and the diver has a bailout gas supply that can be used in such an emergency. The bailout gas carried by the diver may not be sufficient for long decompression, and if this is expected a diving stage or wet bell will be used which carries a larger supply of emergency breathing gas, as well as providing a relatively secure platform for decompression stops.Broken helmet or full-face mask faceplate
The transparent faceplates of most helmets in current use are highly impact resistant and not easily damaged to the extent that they leak dangerously. If this does occur, the free-flow valve can be opened to increase internal pressure to reduce leak flow and purge the helmet of water. Tilting the helmet forward to lower the front will bring the faceplate down and may also reduce leakage and will help purge water from the helmet.Hot water supply failure
In the event of a suit heating water supply failure that cannot be resolved promptly, the diver will abort the dive. This is a serious problem for divers using helium based breathing gas as heat loss is rapid and the risk of hypothermia is high.The diver can adjust the flow rate which can help with small deficiencies in the temperature, but if the flow is shut off or the temperature deviates too much the dive must be aborted before the diver is chilled too much.
Bell emergencies
The bell will be equipped to deal with a bell umbilical failure by switching to onboard emergency gas supply, and the bell will be raised as soon as reasonably possible thereafter. There would be a through-water emergency communications system on a closed bell.In the event of a dynamic positioning runout, the divers would be recalled to the bell and it would be prepared fo lifting on immediate notice, as a severe runout could snag the bell on an obstacle and it could be lost or stuck.
If the bell lifting winch or cable fails and cannot be restored to function, the bell may be recovered using the clump weight winch. If this also fails, a wet transfer abandonment may be possible, in which the divers from the damaged bell are transferred to another closed bell through the water.
The bellman would recover an incapacitated diver to the bell. It may be possible to pull the diver back using the umbilical, but it may be necessary for the bellman to lock out to retrieve the diver.
If the bell will not seal at depth, the divers may need to replace the door seal, and check all valves on through-hull penetrations If may be necessary to return the bell to working depth to assess and work on the problem. If a seal cannot be re-established at depth another bell must be sent down to rescue the divers. If the leak starts at the surface, the supervisor would attempt to maintain internal pressure while the bell would be reconnected to the trunking.
A trapped bell may have to be abandoned. In saturation diving the divers would have to be transferred to another bell.