What is the maximum depth a human can dive to?

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Modern records

A Navy diver submerged 2,000 feet (609.6 m), setting a record using the new Atmospheric Diving System (ADS hardshell suit), off the coast of La Jolla, CA, on Aug. 1 2007.

The deepest open circuit scuba dive was accomplished by Pascal Bernabé (Ralf Tech/WR1 Team) who on July 5, 2005 descended to 1,083 feet (330 m). The dive took place near Propriano, Corsica.

Re-Breather Use

The options for modern exploration are most commonly open circuit scuba and re-breather. Diving is limited by the correct mixture of breathable gases. On open circuit "classic" scuba the gas must be mixed ahead of time, while on re-breathers a diver always has the right mix of gas for the depth. Australian diver David Shaw successfully used a modified recreational re-breather to reach a depth of 888 ft (270 m) in fresh water in 2004. (Shaw died on an attempt to recover a fellow diver's body in 2005.)

Oxygen Requirements

The maximum depth that you can dive safely on air is dependent upon the partial pressure of oxygen. The air that we breathe at the surface is at a partial pressure of 0.2 bar .The partial pressure increases as your depth increases : at 10 metres it will be 0.4 bar and at 20 metres it will be at 0.6 bar. Oxygen becomes toxic at approximately 1.6 bar partial pressure, giving a maximum safe diving depth on ordinary air of around 70 metres (230 ft) . Diving to this extreme depth is not recommended, as individuals tolerances may vary.

Deep-diving Gas Mixtures

The maximum depth someone can dive will be directly related to the percent of oxygen in the breathing mixture. The air mixture we as humans breath is mostly made up of oxygen and nitrogen. The ratio is around 80% nitrogen and 19% oxygen and 1% other gasses. The same gas, oxygen, that keeps us alive can become toxic and kill us under high pressure. But one way to prevent oxygen toxicity is to reduce the concentration of oxygen and replace it with a different gas, such as helium. Since our bodies only use about 5% of the 19% of oxygen in air, we can replace a portion of the gas with something that is relatively safe under pressure. This is called a tri-mix gas. It can be used to dive much deeper than the recreation limit of 130 feet (40 m).

Another physiological problem

As the previous answers all indicate in one way or another, the primary limiting factor in most cases at least is PPO₂ (partial pressure of oxygen) and various gas results including hypothermia, which gases like helium exacerbate. However, in super-high pressures, there is a problem with denaturing of various proteins in the human system. This rare and unlikely problem is still in the books and not reality, as human descent to such depths and ambient pressures has never been tried. When the Trieste descended to 36,000 ft (10,900 m) in 1960 (Marianas Trench), the people inside were protected at one atmosphere. It's likely that with exposure to extremely high pressure, human physiology may fail, for reasons unrelated to gas problems.

Proteins denaturing is detectable by increased neuropathy. Given a "perfect" gas mixture, this could eventually prove fatal. Divers Alert Network (DAN) was the source of this, with the USC Catalina Chamber circa 1970, and may have indicated problems with the medullary sheath as well.

First answer by Mal.j. Last edit by Cjonb. Contributor trust: 838 [recommend contributor]. Question popularity: 186 [recommend question].