How deep is safe to dive?

Answer 1

This is really a loaded question. The deepest dive in history was to 308M or 924FT by John Bennett (Tech Dive Academy, 3/23/10). However, this dive was vastly deeper than the normal 'recreational' depth limits. According to the Scuba industry the recreational depth limit is 130FT or 43M. To reach these depths it is recommended that divers take a Deep-Diving course that works through issues like nitrogen narcosis. New divers are typically told to stay above 65FT. Dives deeper than 130FT fall into the category 'technical', the divers who make these technical dives routinely go into decompression. Decompression is a process in which you slowly allow your body to equalize to the pressures of the water by means of multiple stops at different calculated depths. This is in stark contrast to all recreational diving which is considered no decompression diving.

Now, for your question "How deep is it safe to go when scuba diving?" the answer is strictly dependent on how long you want to go down, and how deep you want to be. A diver can be around 60 feet for about 80 minutes (NAUI Dive Table, 3/23/10). Additionally, safety can be improved by changing the breathing gas. Most recreational diving agencies now have Nitrox, which is a blend of normal air and a controlled amount of Oxygen, which reduces the risk of Nitrogen Narcosis due to lower partial pressures of Nitrogen.

Answer 2

Opinions vary upon how deep one can safely dive on particular gas mixes (subject to proper training), but the following is a summary of generally accepted guidelines:

There are two primary constraints on diving deep on a particular gas mix: risk of narcosis, and risk of oxygen toxicity.

In relation to oxygen toxicity, divers should not use any gas mix which results in them breathing a partial pressure of oxygen greater than 1.4 ATA. For ordinary air, this occurs at 186 feet. For "nitrox" mixes (ie. oxygen enriched air), the depth at which you hit 1.4 ATA can be calculated using the following formulae:

D = ((1.4/FO2) -1) x 33

Where FO2 is the percentage of oxygen in the mix (expressed as a decimal), and D is the depth in feet.

The second limit is narcosis. Opinions on this subject vary considerably. Some people are happy to dive on conventional air up to (and even beyond) the limit of 186 feet recommended for oxygen toxicity. Others argue that this results in a dangerous level of impairment, and is the equivalent to diving whilst heavily intoxicated.

When engaging in very deep diving, most divers reduce the narcotic effect of their breathing gas by diluting it with helium (creating "trimix"). The percentage of helium in the mix will (basically) proportionately reduce the narcotic effect of depth on the diver. Most trimix divers aim for an equivalent narcotic depth of around 100 feet. So if a diver was planning to dive to 240 feet, they would probably blend a mix with 58% helium (reducing 240 feeet by 58% would result in an equivalent nacotic depth of 100 feet).

Remember always that diving deep also carries other risks, such as decompression sickness, and much faster exhaustion of gas supplies.

Answer 3

The world record for diving on a rebreather was set by David Shaw, who dived to a depth of approximately 900 feet. Although Shaw safely completed the dive, he would subsequently die on a subsequent dive to the same depth. On his fatal dive, an attempt was made to rescue Shaw by British diver Don Shirley, and (tellingly) Shirley had to abort the rescue attempt when his rebreather console cracked under the pressure at depth.

Realistically, rebreathers have been used with a reasonable degree of comfort to depths as great as 600 feet. However, beyond that very little testing exists, and many rebreathers will not stand up to the strain exerted on the machine's air spaces by such extreme depths. Only extremely experienced rebreather divers should try to use them beyond the recommended technical diving limit of 330 feet.

Answer 4

It depends how rich the nitrox mix is. Generally speaking, a diver should not dive to any depth where the partial pressure of the oxygen in his breathing mix is greater than 1.4 ATA. You calculate the partial pressure by multiplying the fraction of oxgen in the gas (ie. 32% or whatever) by the total pressure in atmospheres (which is your depth in feet, divided by 33, plus).

So for example, if you were breathing 36% nitrox, your maximum depth should be (1.4 / 0.32) - 1, and then multiply the result by 33 for feet (or by 10, for meters). Which comes to: 4.375 - 1 = 3.375 x 33 = 111 feet.

However, this is subject to the overall limit that you should not generally dive deeper than 130 feet without special training because of the risk of nitrogen narcosis. So even if you were breathing a mix of 24% nitrox, that would give you a notional depth limit of 159 feet, but you would not actually want to go that deep because of other risk factors.

Answer 5

I m not sure but the deepest dive ever is around 300 something meters