Diving safety
Diving safety is the aspect of underwater diving operations and activities concerned with the safety of the participants. The safety of underwater diving depends on four factors: the environment, the equipment, behaviour of the individual diver and performance of the diving team. The underwater environment can impose severe physical and psychological stress on a diver, and is mostly beyond the diver's control. Equipment is used to operate underwater for anything beyond very short periods, and the reliable function of some of the equipment is critical to even short-term survival. Other equipment allows the diver to operate in relative comfort and efficiency, or to remain healthy over the longer term. The performance of the individual diver depends on learned skills, many of which are not intuitive, and the performance of the team depends on competence, communication, preparation, attention and common goals.
There is a large range of hazards to which the diver may be exposed. These each have associated consequences and risks, which should be taken into account during dive planning. Where risks are marginally acceptable it may be possible to mitigate the consequences by setting contingency and emergency plans in place, so that harm can be minimised where reasonably practicable. The acceptable level of risk varies depending on legislation, codes of practice, company policy, and personal choice, with recreational divers having a greater freedom of choice.
In professional diving there is a diving team to support the diving operation, and their primary function is to reduce and mitigate risk to the diver. The diving supervisor for the operation is legally responsible for the safety of the diving team. A diving contractor may have a diving superintendent or a diving safety officer tasked with ensuring the organisation has, and uses, a suitable operations manual to guide their practices. In recreational diving, the dive leader may be partly responsible for diver safety to the extent that the dive briefing is reasonably accurate and does not omit any known hazards that divers in the group can reasonably be expected to be unaware of, and not to lead the group into a known area of unacceptable risk. A certified recreational diver is generally responsible for their own safety, and to a lesser, variable, and poorly defined extent, for the safety of their dive buddy.
The concept of safety
Safety can be, and has been, defined in several ways. The definitions are mostly not contradictory, but are often not fully interchangeable, and it is fairly common for one to be selected to suit the circumstances.Safety is not the absence of accidents. Safety is the presence of defences. Todd Concklin
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. The level of accepted risk may be imposed by a regulatory body, an organisation performing an activity to which risk is connected, or the individual exposed to the risk.
A distinction can be made between three types of safety:
Any combination of the three may coexist. Ideally all three, but the one that matters to the affected population is substantive safety.
Basic principle
A diver should be able to survive any single reasonably predicable incident of significant risk to their life that may plausibly occur under the known and expected circumstances of a planned dive. When this ability is compromised, the dive should be terminated as soon as reasonably practicable, and as safely as reasonably practicable. There are many detailed rules and procedures, and a large amount of equipment dedicated to this principle. Some of these include intervention by another person or team when the potential problem cannot be adequately managed by the unaided diver. The level of acceptable risk will depend on the circumstances and in some cases, the informed choice of the diver.The hazards to which the diver is exposed should be identified during the planning stages of a dive, and the associated risk assessed, and they may be controlled by one or more of several methods, which, in generally accepted order of decreasing priority, are: Elimination of the hazard, substitution of a lesser hazard, engineering controls which provide physical barriers from the hazard, administrative controls which provide procedural barriers, and personal protective equipment which rely on a combination of procedures and equipment where the hazard cannot be sufficiently controlled by other methods. Choice of the method depends to a large extent on whether application to a specific hazard is possible and reasonably practicable.
Environmental factors
The underwater environment is alien to humans. When not actively hostile, it is unforgiving of errors, and some errors can escalate rapidly to a fatal conclusion. Many aspects of the underwater environment are static or predictable, others vary and may not be easily or reliably predictable, and must be managed as and when they occur. The reasonably predictable factors can be allowed for in the dive planning. Suitable equipment can be selected, personnel can be trained in its use and support provided to manage the foreseeable contingencies. When conditions are found to be other than predicted, plans may have to be changed. Sometimes conditions are better than expected, but other times they may be worse, and may deteriorate during the course of a dive to the extent that recovery becomes an emergency.- Predictable and static environmental factors are conditions which should be considered in the dive plan. These include geographic factors, like depth, topography, access, tides and currents, normal temperature range and the local ecology.
- Variable environmental factors are the conditions that can change during a dive, like sea and weather conditions. Dive contingency plans should take into account the reasonably foreseeable variations based on forecasts and local knowledge. When there is no reliable local knowledge available, a wider range of variability should be considered.
- Unknown environmental factors are conditions which cannot be taken into account directly, but their reasonably foreseeable existence should be considered in risk assessment, and allowed for if there is a plausible risk.
Equipment safety
Scuba
Open circuit scuba is mechanically robust and reliable, but can malfunction when damaged, misused, poorly maintained, or occasionally due to unplanned circumstances. Provision of a completely independent emergency supply capable of providing sufficient breathing gas to allow the diver to surface safely from any point on the planned dive profile reduces the risk of a non-survivable out of gas incident to an extremely low level. This remains valid only as long as the emergency gas supply is within immediate reach of the diver, which is more reliably achieved by the diver carrying a bailout cylinder than by relying on a buddy or stand-by diver, who may not be where needed in an emergency.Rebreathers have an intrinsically much higher risk 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. Two thirds of fatalities were associated with high risk behaviour or a high risk dive profile.
Surface-supplied equipment
The essential aspect of surface-supplied diving is that breathing gas is supplied from the surface, either from a diving compressor, high-pressure cylinders, or both. In commercial and military surface-supplied diving, a backup source of breathing gas should always be present in case the primary supply fails. The diver will normally also carry an emergency gas supply. With two alternative air sources available, the surface-supplied diver is much less likely to have an "out-of-gas" emergency than a scuba diver. Surface-supplied diving equipment usually includes voice communication capability with the surface, which improves the safety and efficiency of the working diver. Surface-supplied equipment is required for diving in harsh contaminated environments, and for most commercial diving operations by several professional codes of practice and national regulations.Saturation systems
Design, manufacture, testing and maintenance of saturation diving systems and their components may be required to comply with national occupational safety and health regulations for inshore work and IMCA requirements or the equivalent for offshore work.Saturation systems are generally designed, manufactured, and classified to the standards of a recognised classification society like Lloyd's Register, Bureau Veritas, American Bureau of Shipping or Det Norske Veritas for quality assurance.