Technical diving

Technical diving is scuba diving that exceeds the agency-specified limits of recreational diving for non-professional purposes. Technical diving may expose the diver to hazards beyond those normally associated with recreational diving, and to a greater risk of serious injury or death. Risk may be reduced by using suitable equipment and procedures, which require appropriate knowledge and skills. The required knowledge and skills are preferably developed through specialised training, adequate practice, and experience. The equipment involves breathing gases other than air or standard nitrox mixtures, and multiple gas sources.
Most technical diving is done within the limits of training and previous experience, but by its nature, technical diving includes diving which pushes the boundaries of recognised safe practice, and new equipment and procedures are developed and honed by technical divers in the field. Where these divers are sufficiently knowledgeable, skilled, prepared and lucky, they survive and eventually their experience is integrated into the body of recognised practice.
The popularisation of the term technical diving has been credited to Michael Menduno, who was editor of the diving magazine aquaCorps Journal, but the concept and term, technical diving, go back at least as far as 1977, and divers have been engaging in what is now commonly referred to as technical diving for decades.

Origin

The popular use of the term technical diving can be traced back to the cover story of the first issue of aquaCorps magazine, in early 1990, titled Call it "High-Tech" Diving by Bill Hamilton, describing the current state of recreational diving beyond the generally accepted limits, such as deep, decompression and mixed gas diving. By mid-1991, the magazine was using the term technical diving, as an analogy to the established term technical climbing.
More recently, recognizing that the term was already in use by the Royal Navy for rebreather diving, Hamilton redefined technical diving as diving with more than one breathing gas or with a rebreather. Richard Pyle defined a technical diver as "anyone who routinely conducts dives with staged stops during an ascent as suggested by a given decompression algorithm".
The term technical diving was also used in the US as far back as 1977 by the California Advisory Committee on Scientific and Technical Diving, to distinguish more complex modes of recreational diving from scientific diving for regulatory purposes. In the US the Occupational Safety and Health Administration categorises diving which is not occupational as recreational diving for purposes of exemption from regulation. This is also the case in some other countries, including South Africa. The use of the term technical diving by the CACSTD appears to refer to dives done for technical support of scientific work by occupational divers, and is no longer used for this meaning.
Technical diving emerged between the mid-1980s and the mid-to-late-1990s, and much of the history of its development was recorded in aquaCorps, started by Michael Menduno to provide a forum for these aspects of diving that most recreational diving magazines of the time refused to cover.
At the time, amateur scuba divers were exploring the physiological limits of diving using air. Technical divers looked for ways to extend the limits of air dives, and for ways to extend breathing gas supplies as they went deeper and stayed down longer. The military and commercial diving communities had large budgets, extensive infrastructure, and controlled diving operations, but the amateur diving community had a more trial-and-error approach to the use of mixed gas and rebreathers. Consequently, a relatively large number of fatal incidents occurred during the early years, before a reasonably reliable set of operating procedures and standards began to emerge, making the movement somewhat controversial, both within the mainstream diving establishment and between sectors of the technical diving community.
While the motivation to extend the depth and duration range by military and commercial divers was mainly driven by operational needs to get the job done, the motivation to exceed recreational diving depths and endurance ranges was more driven by the urge to explore otherwise inaccessible places, which could not at the time be reached by any other means.

There are places that no one has been to since the dawn of time. We can’t see what’s there.
We can see what’s on the dark side of the moon or what’s on Mars, but you can’t see what’s in the back of a cave unless you go there.

Sheck Exley, Exley on Mix, aquaCorps #4, Jan 1992

The urge to go where no one has gone before has always been a driving force for explorers, and the 1980s was a time of intense exploration by the cave-diving community, some of whom were doing relatively long air dives in the 60–125 m depth range, and doing decompression on oxygen. The details of many of these dives were not disclosed by the divers as these dives were considered experimental and dangerous. The divers who conducted these dives did not consider them suitable for the ordinary person, but necessary to extend the frontiers of exploration, and there were no consensus guidelines for scuba diving beyond 40 m.

Definition

There is no clear consensus on the definition of technical diving. It is an arbitrary distinction, and the line has been drawn in different places by different organisations, and has shifted on a few occasions. Nitrox diving, rebreather diving and sidemount diving were originally considered technical, but this is no longer the case and most certification agencies now offer these as recreational courses. Some training agencies classify penetration diving in wrecks and caves as technical diving. Even those who agree on the broad definitions of technical diving may disagree on the precise boundaries between technical and recreational diving:

The International Association of Nitrox and Technical Divers has proposed: "Technical diving is a range of knowledge, skills and suitable equipment, which when combined correctly, allow recreational divers to increase their safety while underwater. This information may be employed in either shallow or deep water, may be used to safely extend the divers submerged duration well into the realms of extended decompressions and is often used as a tool for exploration." in their Exploration and Mixed Gas Diving Encyclopedia
The National Association of Underwater Instructors defines technical diving as: "Technical diving is a form of scuba diving that exceeds the typical recreational limits imposed on depth and immersion time. Tec diving involves accelerated decompression and/or the use of variable gas mixtures during a dive."
The National Oceanic and Atmospheric Administration defines technical diving as: "all diving methods that exceed the limits imposed on depth and/or immersion time for recreational scuba diving. Technical diving often involves the use of special gas mixtures for breathing. The type of gas mixture used is determined either by the maximum depth planned for the dive, or by the length of time that the diver intends to spend underwater. While the recommended maximum depth for conventional scuba diving is, technical divers may work in the range of to, sometimes even deeper. Technical diving almost always requires one or more mandatory decompression 'stops' upon ascent, during which the diver may change breathing gas mixes at least once." NOAA does not address issues relating to overhead environments or specify the recreational diving limits in its definition, and the use of single mixture nitrox is well established in mainstream recreational diving.
The Professional Association of Diving Instructors defines technical diving as: "diving other than conventional commercial or recreational diving that takes divers beyond the recreational diving limits of 40 metres/130 feet. It is further defined as an activity that includes one or more of the following: diving beyond 40 metres/130 feet, required stage decompression, diving in an overhead environment beyond 130 linear feet from the surface, accelerated stage decompression and/or the use of multiple gas mixtures in a single dive."
Technical Diving International defines a technical diving as: any dive involving decompression, additional cylinders, alternative breathing gases, rebreathers, or overhead environments such as wrecks, caves or mines. This definition does not make a strong distinction between “recreational” and “technical” as both styles of diving are recreational and require similar equipment.
The Queensland government, Australia, defines recreational technical diving as: recreational diving using nitrox or other mixed gas, or any diving requiring decompression.
The British Sub-Aqua Club defines technical diving as: any diving that involves specialist equipment such as closed circuit rebreathers, using multiple gas mixes on open circuit, or that uses helium-based gas mixtures termed mixed gas.varies from many agencies in including some staged decompression within recreational diving.

Other European diving agencies tend to consider technical diving as dives deeper than and many, as noted for BSAC above, teach staged decompression diving as an integral part of recreational training, rather than as a fundamental change of scope. The Bühlmann tables used by the Sub-Aqua Association and other European agencies make staged decompression dives available, and the SAA teaches modest staged decompression as part of its advanced training programme.

Scope

The following table gives an overview of the activities that various agencies suggest to differentiate between technical and recreational diving:

Activity	Recreational	Technical
Deep diving	Maximum depth of or	Beyond or
Decompression diving	Some agencies define recreational diving as "No decompression" diving; others consider all dives to be decompression dives.	Some agencies define technical diving as "Decompression diving"; others consider all dives to be decompression dives.
Mixed gas diving	Air and nitrox	Nitrox, trimix, heliox and heliair.
Gas switching	Single gas used	May switch between gases to accelerate decompression and/or "travel mixes" to permit descent carrying hypoxic gas mixes
Rebreather diving	Some agencies regard use of semi-closed rebreathers as recreational diving;	PADI TecRec, TDI, GUE, IANTD, SSI XR, IART, ISE, NAUI TEC, PSAI, UTD regard as technical diving.
Wreck diving	Penetration limited to "light zone" or depth + penetration	Deeper penetration
Cave diving	Penetration limited to "light zone" or depth + penetration	Deeper penetration, may involve complex navigation and decompression
Ice diving	Some recreational agencies regard ice diving as recreational diving	Others regard it as technical diving.

Image:Jeffrey Phillips Freeman dives Sardigna nasello 34m.jpg|thumb|An example of wreck diving; A technical diver diving the Nasello wreck in Sardinia at 34m depth.