Equipment in Diver Accidents and Deaths: Part II

Australian experts with the Diving Incident Monitoring Study have analyzed 1,000 scuba diving incidents; 457 involved equipment and, of these, 136 (thirty percent) led to deaths. True equipment malfunctions led to twenty-seven deaths. A 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 manu facturer’s recommendations. That number is much higher than industry-released figures in the United States, which usually absolve TEM as a cause of any diver’s death.

In our April issue, we covered problems associated with BCs, alternate air sources, and masks. Here is our synopsis of the remainder of the study, which appeared in the South Pacific Underwater Medicine Society Journal.

Regulator Problems

Fifty-two of the 457 incidents concerned regulator problems, resulting in eighteen deaths. While some divers believe that first stage failure and low-pressure hose rupture may occur only when the air supply is at maximum pressure, several incidents occurred at depth, well into the dive. Diaphragm first stage regulators are more likely to fail than the piston type because they have an upstream valve that can fail to operate, therefore shutting off the diver’s air supply. Some unbalanced first stage regulators perform poorly at depth. When two divers are sharing one first stage regulator (either balanced or unbalanced) in a shared air situation, the regulator may malfunction even when the tank is not low.

Poor regulator servicing frequently led to problems. Second stages often free flowed after the annual servicing, so a diver should test his or her serviced regulator before diving with it.

Dead divers often have their regulators out of their mouths. Some mouthpieces were torn, a problem that could be eliminated by a visual inspection before each dive. A comfortable and well-fitting mouthpiece would reduce jaw fatigue and accidental displacement during a dive; a line clipping the second stage to the BC would help recovery.

Unnecessary extras (e.g., a humidifier) to the low pressure regulator hose increase the chances of malfunction .

Pressure Gauges

Thirty-seven incidents were related to pressure gauge inaccuracy, which can occur at every stage of a dive — though the majority in this study occurred when tank pressures were low. Annual recalibration and frequent comparisons with buddies’ gauges would help eliminate this problem.

Weights

Divers made several fatal errors with their weights: their belts got snagged on other pieces of equipment, they failed to ditch weights in emergencies, after they took off their belts to leave the water their weights fell off, or weights dropped from BC pockets after being placed there in a hurried attempt to adjust buoyancy.

Many times belts were too long and divers often wrapped the excessive belt lengths around the belts, thereby preventing rapid release. The extra lengths got snagged on the bottom, dislodging the belts and resulting in inevitable uncontrolled rapid ascents.

Fin Loss

One study that analyzed diving fatalities reported that in thirteen percent one or both fins were missing. Fins can be lost with active leg kicks during panic or while swimming against a strong current, especially if they aren’t a snug fit. In several incidents a fin strap broke.

Dive Computers

To prevent sudden power failures, computers should be equipped with either a low battery alarm or a mechanism by which the diver can test battery power before a dive. All divers using computers should dive with an additional timing device, a depth gauge, and a set of tables to calculate decompression requirements (if needed), in case of computer failure.

Safety Sausages

Safety sausages are easily maintained in an upright position in calm conditions, but they’re often invisible and fail to maintain their upright position in adverse conditions. These devices need to be made from a sturdy material and tested in all conditions. All divers should finish the dive with enough air remaining in their air cylinders to handle adverse surface conditions and to fill a safety sausage .

Design Changes Needed

Some incidents reported highlight poor equipment design.

• Co-location of the inflate and deflate mechanisms on the BCD’s inflator hose is ergonomically poor. Inflate and deflate mechanisms need to be separated.

• BC emergency dump valves need to be more accessible.

• Power inflators need a cutoff mechanism.

• Computers need low battery alarms and standardized face layouts.

• Air gauges and tank necks need an audible low pressure alarm.

• Sturdier manufacturing materials are needed in the surf ace sausage signaling devices.

• Lights need to be pressure tested before being sold.

• All battery powered equipment should have either a low battery alarm or a monitor that shows battery status.

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.