What is Technical Diving?
Tech diving describes 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 feet, technical diving may work in the range of 170 to 350 feet and sometimes even deeper.
Divers who are looking to do deep diving or cave diving must frequently learn technical diving skills and rely on technical dive equipment. Whether you're looking for top-of-the-line Dive Rite dry suits, Nitrox capable dive computers, Apollo underwater scooters, or other gear you can relax knowing that you are well outfitted.
Technical diving almost always requires one or more mandatory decompression stops upon ascent, when the diver may change breathing gas mixes at least once. Decompression stops are necessary to allow nitrogen that has accumulated in the diver's tissues to be released in a slow and controlled manner. If a diver exceeds the limits of time and/or depth for recreational diving and ascends too quickly -- large bubbles can form in the tissues, joints, and bloodstream. The formation of these bubbles leads to an extremely painful condition known as Decompression Sickness (DCS), more commonly referred to as the "bends" which can cause paralysis and sometimes even death.
Diving with Nitrox
Divers have used compressed air as their breathing medium since the advent of diving in the 1950s. Its main advantage is ready availability and relatively inexpensive to compress into cylinders. However, air is not the ideal breathing mixture for diving. With a concentration of approximately 79% nitrogen, compressed air poses two potential problems: susceptibility to nitrogen narcosis (a condition resembling alcoholic intoxication) at deeper depths; and decompression sickness (DCS). Both can prove fatal to a diver. In an effort to reduce the ill effects of nitrogen on technical diving, nitrox was developed.
Due to the hazards associated with breathing special gas mixtures, any gas used for breathing other than compressed air, must be placed into specially marked cylinders. Nitrox is a generic term that can be used to describe any gaseous mixture of nitrogen and oxygen. In the context of technical diving, nitrox is a mixture containing more oxygen than air.
While tech diving with nitrox has definite benefits, it also has associated risks. The major hazard is oxygen toxicity which happens when oxygen is inhaled in high concentrations for an extended period of time occurring primarily when a diver exceeds the recreational limits for depth. Under these circumstances, a diver can experience an epileptic-like seizure that may lead to drowning. Due to this potentially fatal hazard, divers using nitrox must adhere to special dive tables listing the maximum safe amount of time that a diver can stay underwater at a certain depth. An Nitrox capable dive computer can help you in this regard.
Mixed-Gas Technical Diving
Mixed-gas diving refers to any activity where the diver breathes a mixture other than air or nitrox. The main incentive to dive with non-air gas mixtures is to avoid nitrogen narcosis. Mixed-gas tech diving can also be beneficial in improving decompression and avoiding oxygen toxicity. Mixed-gas diving operations require detailed planning, sophisticated equipment, and -- at times -- extensive support personnel and facilities. The fact that such technical dives are often conducted at great depths and for extended periods of time increases the risks associated with them. It is extremely important for the breathing mixture to be properly identified, because breathing the wrong mix can be fatal.
One type of mixed gas for technical diving involves the use of heliox. The mixture (helium 79% and oxygen 21%) is often used for very deep tech diving. Unlike nitrogen, helium is not known to have an intoxicating effect at any depth. Heliox has a lower density than nitrogen, making it easier to breathe; and in cases of extended submersion, improves decompression. Still, heliox has drawbacks. It is expensive, has a limited availability, and its thermal conductivity is six times greater than nitrogen, making the diver susceptible to hypothermia.