Equipment in Diver Accidents and Deaths

In America, no one seriously studies the role of equipment in diving accidents and deaths. If the industry has data, it doesn’t release them because it constantly tries to portray diving as no more dangerous than sunbathing. Only the Divers Alert Network makes any effort to discuss the causes of accidents and deaths. However, it doesn’t focus on the circumstances causing the death, but on the medical reasons for the deaths.

But the Aussies, God bless ‘em, think that recreational divers ought to know the facts behind injuries and deaths and regularly study the causes of accidents. Throughout Australia, forms are readily available for divers to report incidents. Those associated with equipment problems (including poor design, poor servicing, a lack of servicing or recalibration, ignorance of the equipment’s function, and equipment misuse) were analyzed by experts with the Diving Incident Monitoring Study. In 1,000 incidents, they found 457 in which equipment played a major role. The following is a synopsis of the study prepared by Chris Acott for the South Pacific Underw a t e r Medicine Society, in whose journal it first appeared.

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The identification and elimination of problems associated with equipment use is an important part of diving safety. While it is inevitable that some equipment will malfunction, other problems will be due to a lack of understanding of equipment function, poor equipment design, poorservicing, equipment misuse, or inadequate post-dive maintenance. These are at best inconvenient, and at worst lethal.

An accident is often the product of unlikely coincidences or errors occurring when there is no system flexibility. It is easier to predict and prevent errors than it is to predict and prevent accidents. Most errors occur repeate d l y, cause no harm, and are recognized and corrected before they become an accident. Identification of errors may suggest corrective strategies that may lead to their reduction or elimination .

True Equipment Failure

We define a diving incident as any error or unplanned event that could or did reduce the safety margin for a diver. An error can be related to anyone associated with the dive and can occur at any stage during the dive.

Equipment misuse occurs when a piece of equipment is used in a manner for which it was not designed or specified. True equipment malfunction (TEM) occurs when a piece of equipment fails to perform in the manner specified by the manufacturer, providing it had been maintained and checked before use according to the manufacturer’s recommendations.

There were 457 incidents involving equipment in the first 1,000 incidents reported. One hundred thirty-six (30 percent) led to deaths. TEM problems resulted in twenty-seven deaths.

In addition to the 154 Buoyancy Control Device (BCD) incidents, there were eleven that were not included because they were related to poor diving technique, e.g. divers frequently using the BCD power inflator to maintain their buoyancy. This led to nine out-of-air (resulting in four deaths) and two low-air problems.

No regulations or standards govern recreational diving equipment. Snorkels are sold without data on their dead space or resistance to breathing. Depth and air gauges are sold without calibration data, although they are assumed to be accurate at the time of purchase. Underwater lights are sold as pressure-resistant and waterproof without any data to validate these statements. An arbitrary recommendation is made that regulators be service dannually, regardless of use. There are also limited data available concerning individual regulator function at various depths and under an increased workload. Divers often assume that a BCD will float an unconscious diver safely on the surface, but this is not always true. The lack of standards has also allowed equipment with a poor ergonomic design to be made available. For example, many BCDs have inflate and deflate buttons co-located on the BCD inflator hose in such a manner that divers have been confused by them during emergencies, leading to further problems .

Equipment problems are common in recreational diving and they are associated with a high incidence of death. They accounted for 46 percent of the incidents reported and 28 percent of all deaths .

One hundred five (10.5 percent) of the 1,000 incidents conform to a definition of TEM, as specified above.

BCD Errors

Errors or problems involving BCDs were the most commonly reported incidents. While nearly a third of these led to deaths, all could have been prevented by the use of one or more corrective strategies .

Furthermore, data concerning the function of a regulator at depth or when the air supply is low should be made available at the time of purchase. This may eliminate ignorance of the time taken to inflate a BCD at depth due to a poorly functioning first stage or when the air cylinder contents are low.

Choosing a correctly sized BCD is important. This will eliminate problems of inadequate buoyancy, restriction of respiration while partially inflated, the possibility that it may become dislodged during diving, and the possibility that it may cover the weight belt (which would reduce access to the weight belt during an emergency).

BCDs are used to adjust a diver ’s buoyancy during a dive. Over-inflation to help raise a heavy object (e.g., an anchor) is an incorrect use of a BCD. These incidents are invariably associated with accidental dropping of the object causing a rapid and uncontrolled Polaris-type ascent with subsequent morbidity. Divers should be taught to achieve buoyancy control without the use of a BCD, how to slow an uncontrolled ascent, and how to respond to a weight belt release in an emergency.

Alternative Air Source Failure s

The use of an alternative air source (a bailout bottle or a separate redundant air cylinder and regulator) may enable a diver who has experienced a regulator failure or any other cause of an out-of-air situation to ascend safel y. However, in some incidents, redundant systems were not checked as frequently as the diver’s major air supply. In these incidents the additional air supply was either turned off, leaked, was empty when needed, or had an inadequate supply of air to allow the diver to ascend safely.

Smaller emergency air bottles, such as Spare Air, which require a filling mechanism to be filled from the major air supply, were available but not used in some incidents because the filling mechanism was unavailable or had failed to work. These smaller bottles contain only a limited amount of air and frequently became depleted during emergency use. Air consumption calculations using the standard 155lb person reveal that to ascend to the surface from 65 ft. at 33 ft./minute, would require a s u rface volume of 5.6 cu. ft. The larger Spare Air contains 3 cu. ft. and is obviously inadequate. It would require a 6 cu. ft. pony bottle to provide enough air for this ascent (provided the tank was at full pressure when first used). A safety stop for three minutes at 16 ft. would require another 8.3 cu. ft. of surface air. The total needed to reach the surface now becomes 17.5 cu. ft.

The addition of another second stage, an octopus regulator, to the first stage regulator is considered to be a part of safe diving practice. This octopus, however, must be positioned so that any diver wishing to breathe from it has easy access; it must be frequently serviced whenever the first and second stages are s e rviced; it must have minimal resistance; and it must be easily purged .

The combination of a secondstage regulator and a low-pressure BCD inflator has no merit. These combinations are extremely difficult to use during an emergency ascent and have resulted in confusion while a diver is trying to breathe from the mouthpiece and deflate the BCD simultaneously. These combinations are also not frequently serviced .

Missing Masks

More than 50 percent of incidents involving mask problems caused deaths. Flooding or dislodgment often caused panic: five of the six incidents involving mask flooding and panic resulted in diver harm; two of the three incidents involving mask clearing and panic caused death. Six of the ten incidents in which the diver’s mask was dislodged resulted in death, although only one was associated with panic. Mask problems have been reported as a contributing factor in 5 percent of recreational deaths. Clearly, mask clearing and the ability to continue a dive without a mask are essential skills that must be mastered by all divers.

Next issue: regulators, weight belts, and more

The author of this study, Dr. C.J. Acott, is coordinator of the Diving Incident Monitoring Study (DIMS) and director of diving medicine, Royal Adelaide Hospital Hyperbaric Medicine Unit, Royal Adelaide Hospital, North Terrace, Adelaide, South Australia.