Diving safety
Where risks are marginally acceptable it may be possible to mitigate the consequences by setting contingency and emergency plans in place, so that damage can be minimised where reasonably practicable.
Todd Concklin [3] Safety is the condition of being protected from harm, and also refers to the control of recognized hazards in order to achieve an acceptable level of risk.
When one operates where it is not feasible to avoid or remove hazards completely, safety implies that defences have been set up to recover from foreseeable incidents and to mitigate their consequences to an acceptable level.
Open circuit scuba is mechanically robust and reliable, but can malfunction when damaged, misused, poorly maintained, or occasionally due to unplanned circumstances.
[7][8] Rebreathers have an intrinsically much higher risk[9] of mechanical and electrochemical sensor failure than open circuit scuba because of their structural and functional complexity, and some inherent characteristics of electro-galvanic oxygen sensors, but this can be mitigated by fault tolerant design which provides redundancy of critical items and by carrying sufficient alternative breathing gas supplies for bailout including any required decompression in case of failure.
Designs that minimize risk of human-machine interface errors, and adequate training in procedures that deal with this area may help reduce the fatality rate.
The remaining fatalities probably arose as a result of a progressive sequence of events involving two or more procedural errors or equipment failures, and since procedural errors are generally avoidable by a well-trained, intelligent and alert diver, working in an organised structure, and not under excessive stress, it was concluded that the low accident rate in professional scuba diving is due to this factor.
While working underwater, divers are subjected to high levels of physical and psychological stress due to environmental conditions and the limitations of the life support systems, as well as the rigours of the task at hand.
Improvements in training standards and equipment design and configuration, and increased awareness of the risks of diving, have not eliminated fatal incidents, which occur every year in what is generally a reasonably safe recreational activity.
Some conditions affect fitness to function safely and effectively underwater in unpredictable ways, and may not be noticed until they show up under stress and precipitate an emergency.
[13] The primary purpose of a professional diving team is to improve safety for the working diver by providing backup and support, and to manage the surface equipment required for the operation.
This trade-off is acknowledged in occupational health and safety legislation, where precautions are required to be reasonably practicable, with reference to cost, benefit, available technology and other factors.
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.
General environmental conditions can lead to another group of disorders, which include hypothermia and motion sickness, injuries by marine and aquatic organisms, contaminated waters, man-made hazards, and ergonomic problems with equipment and tasks.
There are a growing number of commercial, military and scientific applications where a remotely operated or autonomous underwater vehicle can produce satisfactory results.
To a lesser extent this applies to atmospheric pressure diving, where the diver is not exposed to the environment as long as the suit integrity is maintained, but some hazards and risks remain.
There is a point at which closed circuit bailout becomes a more manageable option, and the requirement for ability to return safely from any point on the planned dive profile makes it necessary for the breathing loop and gas supplies to be fully independent, though the ability to make use of the primary gas supply in the bailout rebreather can considerably extend the range for a small added complexity, using highly reliable components, but adding to the task loading of the diver.
The current generation of atmospheric suits are more ergonomically flexible than earlier versions, but are still very limited in personal mobility and dexterity compared to an ambient pressure diver.
[67] ROVs are commonly used in deep water industries such as offshore hydrocarbon extraction, where they can carry out many tasks previously requiring diver intervention.
In most jurisdictions, recreational diving is unregulated, and an entirely untrained person is not legally hindered from scuba or freediving at their own risk in public access bodies of water.
The exemption was written to include the ability to deviate from safe diving practices under limited conditions where compliance would be impracticable due to time constraints or the possible consequences of failing to perform the task overwhelm the risks taken using available facilities.
This exclusion does not apply during training, recovery operations, searches where there is no reasonable probability of rescue of a living person or there is no real and immediate public safety hazard.
These documents provide much of the necessary detail of how frequently encountered tasks should be performed, using methods which have been tested and found to be effective, efficient and acceptably safe.
These are reminders to make critical checks for people who are well aware of the need, and highly skilled and responsible posts such as airline cockpit crew and operating theatre staff, who nevertheless occasionally fail to complete the necessary preparations in the absence of a checklist.
These skill sets are the basis of the standard operating procedures, and have themselves been standardised to a degree where they are largely internationally accepted, and are portable between organisations without requiring much re-learning.
The diver should be able to manage a reasonably foreseeable and immediately life-threatening emergency unaided as there can be no guarantee that someone else will be near enough to help, will notice and will respond appropriately in time.
Buddy and team diving procedures impose a significant additional task loading on the divers, particularly in adverse conditions, such as darkness, low visibility, confined spaces, strong currents, cold water and unfamiliarity with each other's equipment and habits.
[94] When professional divers dive as buddy pairs their responsibility to each other is specified as part of the standard operating procedures, code of practice, or governing legislation.
[42][96][74][73][97] Analysis of rebreather diving incidents shows that full-face masks and mouthpiece retaining straps are effective for protecting the airway if a diver loses consciousness underwater due to breathing an inappropriate gas mixture, the most common disabling agent.
Valuable understanding of the risks of diving can be derived from analysis of such incidents, but they are a small fraction of the potential learning opportunities because for each documented accident there are estimated to be possibly hundreds of undocumented near-misses.
