Diving longer and deeper safely
There are a number of techniques to increase the diver's ability to dive deeper and longer:

technical diving - diving deeper than 40 metres (130 ft) and/or using mixed gases.
surface supplied diving - use of umbilical gas supply and diving helmets.
saturation diving - long-term use of underwater habitats under pressure and a gradual release of pressure over several days in a decompression chamber at the end of a dive
Unknown - 16 years, 9 months, 15 days ago

Diving longer and deeper safely
There are a number of techniques to increase the diver's ability to dive deeper and longer:

technical diving - diving deeper than 40 metres (130 ft) and/or using mixed gases.
surface supplied diving - use of umbilical gas supply and diving helmets.
saturation diving - long-term use of underwater habitats under pressure and a gradual release of pressure over several days in a decompression chamber at the end of a dive
Unknown - 16 years, 9 months, 15 days ago

Oxygen toxicity
Oxygen toxicity occurs when oxygen in the body exceeds a safe "partial pressure" (PPO2). In extreme cases it affects the central nervous system and causes a seizure, which can result in the diver spitting out his regulator and drowning. Oxygen toxicity is preventable provided one never exceeds the established maximum depth of a given breathing gas. For deep dives, (generally past 130 feet / 39 meters) "hypoxic blends" containing a lower percentage of oxygen than atmospheric air are used. For more information, see Oxygen toxicity.


Unknown - 16 years, 9 months, 15 days ago

In the "single-hose" two-stage design, the first stage regulator reduces the cylinder pressure of about 200 bar (3000 psi) to an intermediate level of about 10 bar (145 psi) The second stage demand valve regulator, connected via a low pressure hose to the first stage, delivers the breathing gas at the correct ambient pressure to the diver's mouth and lungs. The diver's exhaled gases are exhausted directly to the environment as waste. The first stage typically has at least one outlet delivering breathing gas at unreduced tank pressure. This is connected to the diver's pressure gauge or computer, in order to show how much breathing gas remains.
Unknown - 16 years, 9 months, 15 days ago

Open-circuit
The most commonly used scuba set today is the "single-hose" open circuit 2-stage diving regulator, coupled to a single pressurized gas cylinder, with the first stage on the cylinder and the second stage at the mouthpiece. This arrangement differs from Emile Gagnan's and Jacques Cousteau's original 1942 "twin-hose" design, known as the Aqua-lung, in which the cylinder's pressure was reduced to ambient pressure in one or two or three stages which were all on the cylinder. The "single-hose" system has significant advantages over the original system.

Unknown - 16 years, 9 months, 15 days ago