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Technical diver during a decompression stop.

Technical diving (sometimes referred to as Tec diving) is a form of scuba diving that exceeds the scope of recreational diving (although the vast majority of technical divers dive for recreation and nothing else). Technical divers require advanced training, extensive experience, specialized equipment and often breathe breathing gases other than air or standard nitrox.[1]

The concept and term 'technical diving' are both relatively recent advents,[note 1] although divers have been engaging in what is now commonly referred to as technical diving for decades. The term "technical diving" was first coined by Michael Menduno, editor of (now defunct) diving magazine AquaCorps in 1991.[2]


Definition of 'technical diving'

There is some level of professional disagreement as to what the term should encompass.[3][4][5] It was not that many years ago that NITROX diving was considered "technical"; however today NITROX is not normally considered technical. Some say that technical diving is any type of SCUBA that is considered higher risk than conventional recreational diving. However, some advocate that this should include penetration diving (as opposed to open-water diving), whereas others contend that pentrating overhead environments should be regarded as a separate type of diving. Others seek to define technical diving solely by reference to the use of decompression.[note 2] Certain minority views contend that certain non-specific higher risk factors should cause diving to be classed 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.

  • PADI, the largest recreational diver training agency in North America, defines technical diving as "diving other than conventional commercial or recreational diving that takes divers beyond recreational diving limits. It is further defined as an activity that includes one or more of the following: diving beyond 40 meters/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."[6]
  • NOAA defines technical diving in this way: "Technical diving is a term used to describe 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 (other than compressed air) 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 130 ft, technical divers may work in the range of 170 ft to 350 ft, 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."[7] NOAA does not address issues relating to overhead environments in its definition.

The following table tries to set out the broad indicative parameters of what is normally regarded as technical rather than recreational diving.

Technical Diving
Activity Recreational Technical
Deep diving Maximum depth of 40 metres/130 feet[note 3] Below 40 metres/130 feet
Decompression diving[note 4] No decompression Decompression diving
Mixed gas diving Air and Nitrox Trimix, Heliox, Heliair and Hydrox
Gas switching Single gas used May switch between gases to accelerate decompression and/or "travel mixes" to permit descent carrying hypoxic gas mixes
Wreck diving Penetration limited to "light zone" or 30 metres/
100 foot depth/penetration
Deeper penetration
Cave diving Penetration limited to "light zone" or 30 metres/
100 foot depth/penetration[note 5]
Deeper penetration
Ice diving Some agencies regard ice diving as recreational diving;PADI others as technical diving.NAUI
Rebreathers Some agencies regard use of semi-closed rebreathers as recreational diving;PADI others as technical diving.NAUI
Solo diving Recreational diving requires buddy system Solo diving[note 6]


Diver returning from a 600ft dive

Technical dives may be defined as being either dives to depths deeper than 130 feet / 40 meters or dives in an overhead environment with no direct access to the surface or natural light. Such environments may include fresh and saltwater caves and the interior of shipwrecks. In many cases, technical dives also include planned decompression carried out over a number of stages during a controlled ascent to the surface at the end of the dive.

The depth-based definition is derived from the fact that breathing regular air while experiencing pressures causes a progressively increasing amount of impairment due to nitrogen narcosis that normally becomes serious at depths of 100 feet / 30 metres or greater. Increasing pressure at depth also increases the risk of oxygen toxicity based on the partial pressure of oxygen in the breathing mixture. For this reason technical diving often includes the use of breathing mixtures other than air.

These factors increase the level of risk and training required for technical diving far beyond that required for recreational diving. This is a fairly conservative definition of technical diving.

Inability to ascend directly

Technical dives may alternatively be defined as dives where the diver cannot safely ascend directly to the surface either due to a mandatory decompression stop or a physical ceiling. This form of diving implies a much larger reliance on redundant equipment and training since the diver must stay underwater until it is safe to ascend or the diver has left the overhead environment.

Decompression stops

Free floating decompression stop.

A diver at the end of a long or deep dive may need to do decompression stops to avoid decompression sickness, also known as the "bends". Metabolically inert gases in the diver's breathing gas, such as nitrogen and helium, are absorbed into body tissues when breathed under high pressure during the deep phase of the dive. These dissolved gases must slowly be released from body tissues by pausing or "doing stops" at various depths during the ascent to the surface. In recent years most technical divers have greatly increased the depth of the first stops, so as to reduce the risk of bubble formation before the [more traditional] long shallow stops. Most technical divers breathe enriched oxygen breathing gas mixtures such as nitrox during the beginning and ending portion of the dive. To avoid nitrogen narcosis while at maximum depth it is common to use trimix which adds a percentage of helium replacing nitrogen to the diver's breathing mixture. Pure oxygen is then used during shallow decompression stops to reduce the time needed by the diver to effectively rid themselves most of remaining excess inert gas in their body tissues and reducing the risk of "the bends." Surface intervals are usually required to prevent the residual nitrogen from building up to dangerous levels on subsequent dives.

Physical ceiling

These types of overhead diving can prevent the diver surfacing directly:

Extremely Limited Visibility

Technical dives in waters where the diver's vision is severely impeded by low-light conditions, caused by silt or depth, require an elevated level of aptitude because of the knowledge and skill required to operate in such an environment, and because visibility impairments are often caused by moving water currents. The combination of low visibility and swift current make these technical dives extremely risky to all but the most skilled and well-equipped divers.

Gas mixes

Technical dives may also be defined by the use of hypoxic breathing gas mixtures other than air such as trimix, heliox, and heliair. This definition is derived from the fact that breathing a mixture with the same oxygen concentration as is found in air (roughly 21%) at depths greater than 180 feet / 55 meters results in a very rapidly increasing risk of severe symptoms of oxygen toxicity. The first sign of oxygen toxicity is usually a convulsion without warning. This convulsion usually results in a fatal accident, as the regulator falls out and the victim drowns. Sometimes the victim may get warning symptoms prior to the convulsion. These can include visual and auditory hallucinations, nausea, twitching (especially in the face and hands), irritibility and mood swings and dizziness. Increasing pressure due to depth also causes nitrogen to become narcotic, resulting in a reduced ability to react or think clearly (see Nitrogen narcosis). By adding helium to the breathing mix, divers can reduce these effects, as helium does not have the same narcotic properties at depth. These gas mixes can also lower the level of oxygen in the mix to reduce the danger of oxygen toxicity. Once the oxygen is reduced below 18% the mix is known as a hypoxic mix as it doesn't contain enough oxygen to be used safely at the surface.

Nitrox is another common gas mix, and while it is not used for deep diving, it decreases the build up of nitrogen within the diver's body by increasing the percentage of oxygen. This reduces the nitrogen percentage, as well as allowing for a greater number of multiple dives vs "standard" air. The depth limit of Nitrox is governed by the percentage of oxygen used, as there are multiple oxygen percentages available in nitrox. Further training and knowledge is required in order to safely use and understand the effects of these gases on the body in a diving situation.

"Deep air"/extended range diving

One of more divisive subjects in technical diving relates to using compressed air as a breathing gas on dives below 130 feet/40 meters.[8] Whilst the largest technical diver training agencies still promote and teach such courses (TDI[9], IANTD and DSAT/PADI), there is an increasingly vocal minority (NAUI Tec, GUE, UTD) which argues that diving deeper on air is unacceptably risky, and argue that helium mixes should be used for dives beyond a certain limit (100 - 130 feet, depending upon agency). Such courses used to be referred to as "deep air" courses, but are now commonly called "extended range" courses.

Deep air proponents base the proper depth limit of air diving upon the risk of oxygen toxicity. Accordingly, they view the limit as being the depth at which partial pressure of oxygen reaches 1.4 ATA (which occurs at about 186 feet/50 metres). Helitrox/triox proponents argue that the defining risk should be nitrogen narcosis, and suggest that when the partial pressure of nitrogen reaches approximately 4.0 ATA (which occurs at about 125 feet/38 meters) helium is necessary to offset the effects of the narcosis.

DAN does not formally reject deep air diving per se, but it is keen to point out a number of additional risks which such diving involves.[10]


Technical diver with decompression gases in side mounted stage cylinders.

Technical divers may also use various forms of less common diving equipment to accomplish their goals. Typically technical dives involve significantly longer durations than average recreational scuba dives. As decompression stops act as a virtual overhead, preventing a diver with a problem from surfacing immediately, there is a need for redundant equipment. Technical divers usually carry at least two tanks, each with its own regulator. In the event of a failure, the second tank and regulator acts as a back-up system. Technical divers therefore increase their supply of available breathing gas by either connecting multiple high capacity diving cylinders and/or by using a rebreather. The technical diver may also carry additional cylinders, known as stage bottles, to ensure adequate breathing gas supply for decompression with a reserve for bail-out in case of failure of their primary breathing gas. The stage cylinders are normally carried using an adaptation of a sidemount configuration.


Technical diving requires specialised equipment and training. There are many technical training organisations: see the Technical Diving section of List of diver training organizations. Technical Diving International (TDI), Global Underwater Explorers (GUE), International Association of Nitrox and Technical Divers (IANTD) and National Association of Underwater Instructors (NAUI) seem to be popular as of 2009. Recent entries into the market include Unified Team Diving (UTD), and Diving Science and Technology (DSAT), the technical arm of Professional Association of Diving Instructors (PADI). The Scuba Schools International (SSI) Technical Diving Program (TechXR - Technical eXtended Range) was launched in 2005.[11]

British Sub-Aqua Club (BSAC) training has always had a technical element to its higher qualifications, however it has recently begun to introduce more technical level Skill Development Courses into all its training schemes, by introducing technical awareness into its lowest level qualification of Ocean Diver, for example, nitrox will become mandatory. It has also recently introduced trimix qualifications and continues to develop closed circuit training.

See also


  1. ^ Richardson, Drew (2003). "Taking 'tec' to 'rec': the future of technical diving". South Pacific Underwater Medicine Society Journal 33 (4). Retrieved 2009-08-07.  
  2. ^ Bret Gilliam. "Deep Diving". Retrieved 2009-09-14.   at page 15.
  3. ^ Gorman, Des F (1992). "High-tech diving". South Pacific Underwater Medicine Society Journal 22 (1).  
  4. ^ Gorman, Des F (1995). "Safe Limits: A International Dive Symposium. Introduction.". South Pacific Underwater Medicine Society Journal 25 (1). Retrieved 2009-08-07.  
  5. ^ Hamilton Jr, RW (1996). "What is technical diving? (letter to editor)". South Pacific Underwater Medicine Society Journal 26 (1). Retrieved 2009-08-07.  
  6. ^ PADI, Enriched Air Diving, page 91. ISBN 978-1-878663-31-3
  7. ^ "Technical Diving". NOAA. February 24, 2006. Retrieved 2008-09-25.  
  8. ^ "Deep Air IS Stupdity". Retrieved 2009-09-03.  
  9. ^ "TDI - Extended Range Diver". Retrieved 2009-09-03.  
  10. ^ John Lippmann, DAN. "How deep is too deep?". Retrieved 2009-09-03.  
  11. ^ "SSI TechXR - Technical diving program". Scuba Schools International. Retrieved 2009-06-22.  


  1. ^ In his 1989 book, Advanced Wreck Diving, author and leading technical diver, Gary Gentile, commented that there was no accepted term for divers who dived beyond agency-specified recreational limits for non-professional purposes. Revised editions use the term "technical diving", and Gary Gentile published a further book in 1999 entitled The Technical Diving Handbook.
  2. ^ As most technical diving training agencies point out, references to "decompression diving" is a misnomer, as all dives involve an element of decompression as the diver off-gases. However, the term decompression diving is often used to describe diving which involves one or more mandatory decompression stops prior to surfacing.
  3. ^ Most recreational diving agencies recommend diving no deeper than 30 meters/100 feet, and suggest an absolute limit of 40 m/130 feet.[1]
  4. ^ There is a reasonable body of professional opinion that considers decompression diving to be the sole differentiator for "technical" diving.SSI
  5. ^ Some certification agencies prefer to the term "cavern diving" to cave penetration within recreational diving limits.
  6. ^ Some training agencies regard solo diving within the "recreational" sphere.SDI

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