 Beginning with Alexander the Great and continuing through to modern times, mankind has struggled to do two things when it comes to staying underwater: dive deeper, and stay longer.
To a great degree, the type of equipment being utilized limits diving depth. Typical open circuit scuba, of the type popularized by Jacques Cousteau], has a generally recognized operational depth limit of 130 fsw / 40 msw*. While it has been used deeper (the current record is 1,082 fsw / 330 msw), limitations imposed by gas volumes and decompression requirements make it unreasonable for working dives at depths beyond those stated above.
* Fsw = feet of seawater, or the depth of a diver in feet. Msw = meters of seawater, or the depth of a diver measured in meters.
For a diver wearing a helmet supplying breathing gas from the surface (the typical “deep sea” diver portrayed wearing a large brass helmet), depth is limited by the type of gas being breathed, and again by decompression requirements. If air is being used, then maximum operational depth is about 200 fsw / 60 msw. If helium is used to replace the portion of air comprised of nitrogen, then that depth increases to about 300 fsw / 90 msw.
While bounce dives have been made to a depth of 600 fsw /180 msw using traditional diving dress, most dives conducted at depths deeper than this have mandated the use of saturation diving systems. Divers compress (descend) in a chamber, and then are ferried down to working depths of up to about 1700 fsw / 540 msw. Divers move from the surface to working depth and back again in a personnel transfer chamber (PTC), which essentially is a thick steel cylinder lowered on the end of a cable. There are two major problems with this type of diving: decompression and mobility.
When they complete their work at depth, the divers are brought back to the surface in the PTC, and move back into a chamber. The chamber then slowly ascends to the surface, allowing the divers to decompress the entire time. The decompression process may take as long as three weeks.
 What is decompression? As the pressure surrounding divers increases as they descend, some of the gas they are breathing dissolves into their tissues. The deeper they are, or the longer they stay, the greater the amount of dissolved gas.When they ascend, this gas comes out of solution. If they ascend slowly enough, then this gas is expelled from the body as they breathe. However, if they come up quickly, then this gas “pops” out of solution, and forms bubbles in the body. This is called “decompression sickness,” and depending on the quantity and location of the bubbles can be completely debilitating, or even lead to death. If you visualize opening a bottle of soda after shaking it, you can understand what the effects in the human body are. As noted earlier, it can take as long as three weeks to remove this dissolved gas from the body safely.
 When working underwater at depth, the divers have different issues. One is the issue of breathing gas recovery. As noted in “”, the helium used by the divers is extremely expensive. To minimize this cost, most deep-sea operations tether the divers to the PTC with an umbilical hose that reclaims most of the gas they exhale. This cable is cumbersome, though, and severely limits mobility and the divers’ ability to work while underwater.
Developing technologies, such as those being developed by Blu Vu, will ameliorate these and other issues. Compact, reliable, assisted breathing apparatuses now in development will minimize decompression obligations while at the same time increasing diver mobility and decreasing overall workload.
Blu Vu technology will allow divers to consistently work at deeper depths for longer times, with greater comfort and safety, and with a significantly higher productivity than current technologies.
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