Everything about Technical Diving totally explained
Technical diving is a form of
scuba diving that exceeds the scope of
recreational diving. Technical divers require advanced training, extensive experience, mixed
gases and specialized equipment.
Definition of 'technical diving'
Several factors lead to a dive being classed as a 'technical dive'.
Depth
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 can't 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's safe to ascend or the diver has left the overhead environment.
Decompression stops
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 [moretraditional] 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's 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 of all remaining excess inert gas in their body tissues and reducing the risk of the "bends".
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
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 doesn't 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 isn't 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, and is thus classed as a technical diving mix.
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.
Equipment
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's a need for redundant equipment. Technical divers usually carry at least two tanks, each with their 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.
Training
Technical diving requires specialised equipment and training. There are many technical training organisations: see the Technical Diving section of
List of diver training organizations.
TDI
,
GUE,
IANTD and
NAUI seem to be popular at the time of writing. Recent entries into the market include
DSAT, the technical arm of
PADI. The
SSI Techical Diving Program
TechXR - Technical eXtended Range] was launched in 2005.
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.
Further Information
Get more info on 'Technical Diving'.
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