Cave Diving - Safety

Safety

Most cave divers recognize five general rules or contributing factors for safe cave diving, which were popularized, adapted and became generally accepted from Sheck Exley's 1977 publication Basic Cave Diving: A Blueprint for Survival. In this book, Exley included accounts of actual cave diving accidents, and followed each one with a breakdown of what factors contributed to the accident. Despite the uniqueness of any individual accident, Exley found that at least one of a small number of major factors contributed to each one. This technique for breaking down accident reports and finding common causes among them is now called Accident Analysis, and is taught in introductory cave diving courses. Exley outlined a number of these resulting cave diving rules, but today these five are the most recognized:

• Training: A safe cave diver never exceeds the boundaries of his/her training. Cave diving is normally taught in segments, each successive segment focusing on more complex aspects of cave diving. Furthermore, each segment of training must be coupled with real world experience before moving to a more advanced level. Accident analysis of recent cave diving fatalities has proven that academic training without sufficient real world experience is not enough in the event of an underwater emergency. Only by slowly building experience can one remain calm enough to recall their training should a problem arise, whereas an inexperienced diver (who may be recently trained) will tend to panic when confronted with a similar situation.

• Guide line: A continuous guide line is maintained at all times between the leader of a dive team and a fixed point selected outside the cave entrance in open water. Often this line is tied off a second time as a backup directly inside the cavern zone. As the dive leader lays the guideline he takes great care to ensure there is sufficient tension on the line. Should a silt out occur, divers can find the taut line and successfully follow it back to the cave entrance. Failure to use a continuous guide line to open water is cited as the most frequent cause of fatality among untrained, non-certified divers who venture into caves.

• Depth rules: Gas consumption and decompression obligation increase with depth, and it is critical that no cave diver exceeds the dive plan or the maximum operating depth (MOD) of the gas mixture used. Also, the effects of nitrogen narcosis are more critical in a cave, even for a diver who has the same depth experience in open water. Cave divers are advised not to dive to "excessive depth," and to keep in mind this effective difference between open water depth and cave depth. It should be noted that among fully trained cave divers' deaths, excessive depth is frequently cited as the cause.

• Air (gas) management: The most common protocol is the 'rule of thirds,' in which one third of the initial gas supply is used for ingress, one third for egress, and one third to support another team member in the case of an emergency. UK practice is to adhere to the rule of thirds, but with an added emphasis on keeping depletion of your separate air systems "balanced," so that the loss of a complete air system will still leave you with sufficient air to return safely. Note that the rule of thirds makes no allowance for the increased air consumption that the stress caused by the loss of an air system will induce. Dissimilar tank sizes among the divers are also not included and the proper amount of air reserve must be calculated for each dive (if tanks are dissimilar). UK practice is to assume that anyone else diving with you does not exist, as in a typical UK sump there is absolutely nothing that you can do to assist him/her. Most UK cave divers dive solo. US sump divers follow a similar protocol. Note that the rule of thirds was devised as an approach to diving Florida's caves - they typically have high outflow currents, which help to reduce air consumption when exiting. In a cave system with little (or no) outflow it is mandatory to reserve more air than is dictated by the rule of thirds.

• Lights: Each cave diver must have three independent sources of light. One is considered the primary and the other two are considered backup lights. Each light must have an expected burn time of at least the planned duration of the dive. If any one of the three light sources fail for one diver, the dive is called off and ended for all members of the dive team.

These five rules may be remembered with the mnemonic The Good Divers Are Living, the first letter of each word referring to the first letter of the corresponding rule. An alternative mnemonic taught in the United States is Thank Goodness All Divers Live, requiring a rearrangement of the rules.

In recent years new contributing factors were considered after reviewing accidents involving solo diving, diving with incapable dive partners, video or photography in caves, complex cave dives and cave diving in large groups. With the establishment of technical diving, the usage of mixed gases—such as trimix for bottom gas, and nitrox and oxygen for decompression—reduces the margin for error. Accident analysis informs us that breathing the wrong gas at the wrong depth and/or not analyzing the breathing gas properly has led to cave diving accidents.

Cave diving requires a wide variety of very specialized techniques. Divers who do not adhere strictly to these techniques, as well as equipment specifications, greatly increase the amount of risk they undertake. The cave diving community works hard to educate the public on the risks they assume when they enter water-filled caves. Warning signs with the likenesses of the Grim Reaper have been placed just inside the openings of many popular caves in the US, and others have been placed in nearby parking lots and local dive shops.

Many cave diving sites around the world contain basins, which are also popular open-water diving sites. These sites try to minimize the risk of untrained divers being tempted to venture inside the cave systems. With the support of the cave diving community, many of these sites enforce a "no-lights rule" for divers who lack cave training—they may not carry any lights into the water with them. It is easy to venture into an underwater cave with a light and not realize how far away from the entrance (and daylight) one has swum; this rule is based on the theory that, without a light, divers will not venture beyond daylight.

New available technology and diver experience are no longer matching the initial phase of local cave diving accident analysis. In the early phases the analysis shows that 90% of accidents were not trained cave divers; from the 2000s on the trend has reversed to 80% of accidents involving trained cave divers. Modern cave divers' capability and available technology allows them to venture well beyond traditional limits and into actual exploration. The result is an increase of cave diving accidents in 2011 which tripled the yearly average of 2.5 fatalities a year. Unfortunately in the first half of 2012, the 2011 accident rate has already been surpassed. In response in Jan 2012 IDREO (www.idreo.org) was created in order to increase awareness of the current situation, by listing current worldwide accidents by year in real time and promoting a community discussion and analysis of accidents thru a yearly Cave Diver Safety Meeting.