Snorkling with emergency air tank

Quote: Pacomartin

I said it was very unlikely that you could get the bends with these devices as you would have to have your friends pass you one after another until you had at least two dozen.

I was thinking more of a rich neophyte who simply surfaced briefly, obtained a new bottle and went back down. Does seem unlikely to be more than a four hour activity for even an enthusiast.

Pure oxygen is always fatal as its the carbonic acid from the CO2 that induces breathing.

Quote: Fleastiff

Pure oxygen is always fatal as its the carbonic acid from the CO2 that induces breathing.

I never heard of that.


Nitrogen can cause bubbles (i.e. the bends) and also cause a diver to be "narced" (short for nitrogen narcosis) which simulates effects of being very drunk and makes you vulnerable to making stupid errors.

Nitrogen effects are at lower depths than oxygen effects. Recreational SCUBA divers are limited to depths less than 130' on pure air, although lawyers are more likely to push for 100' for commercial recreational operations. Industrial divers used to have a 175 ft limitation before the ship had to have a chamber onboard (a very expensive addition). As a practical matter no industrial operation wants to deal with an onboard hyperbaric chamber, and they attempt almost all operations at deeper depths with remotely operated vehicles.

However, Oxygen toxicity can result in seizures and sudden convulsions and unconsciousness, during which victims can lose their regulator and drown.

But diving below 184 ft on air would expose a diver to increasing danger of oxygen toxicity as the partial pressure of oxygen exceeds 1.4 bar (140 kPa).

Enriched Air Nitrox (EANx) can cause oxygen toxicity at shallower depths when compared to air. The advantage of Nitrox is it can be used to shorten decompression stops by drawing dissolved inert gases out of the body more quickly. You can also increase dive time, and most people believe you have a lower chance of getting a headache. Recreational divers can legally use up to 50% oxygen, but most recreational operations stick to 33% to be safe. Only Navy Seals would dare to breathe pure oxygen underwater because the danger of death is so incredibly high. Even a SEAL would try to maintain diving depths of 20 feet or less. The advantage of pure oxygen is you could stay underwater for 8-12 hours and complete a sabotage mission. But that is a long time to concentrate as even a momentary deviation in depth could be fatal.

Quote: Pacomartin

I never heard of that.

CO2 levels are important. Pulse oximeters are often used in doctors offices, ambulances and hospitals to measure oxygen levels in the fingers and thereby provide estimates of oxygen levels elsewhere in the body. Sometimes actual blood gases are measured. A tricky and more expensive procedure.

Of increasingly greater utility are capnography devices that show not only oxygen levels but also carbon dioxide levels since it can be critical. The brain's instructions to breathe depend on levels of carbonic acid which is CO2 dissolved in the blood.

Sales of capnography equipment are likely to increase far more than the sales of pulse oximeters.

Quote: Pacomartin

It just takes a lot of time at only 10 meters.

thanks. I didn't know that. I thought depth was the determining factor.

Quote:

The original cases of the bends in the 1840's involved workers who were under pressure for 7 hours at a time.

I recall reading about that. It was in underwater tunnels, right? Underwater tunnel meaning a tunnel that runs under the floor of a river, lake or sea. I wonder how the pressure works in such cases.

Quote:

I said it was very unlikely that you could get the bends with these devices as you would have to have your friends pass you one after another until you had at least two dozen.

I have one phrase for you "Here, hold my beer." (reportedly Theresa May said it right before calling the snap election, too).

Dangers from breathing pure oxygen AT NORMAL PRESSURE are from time intervals much longer than those associated with diving.

Quote: Copyright © 2017 HowStuffWorks

Now what would happen if you breathed 100 percent oxygen?

In guinea pigs exposed to 100 percent oxygen at normal air pressure for 48 hours, fluid accumulates in the lungs and the epithelial cells lining the alveoli. In addition, the pulmonary capillaries get damaged. A highly reactive form of the oxygen molecule, called the oxygen free radical, which destroys proteins and membranes in the epithelial cells, probably causes this damage.

In humans breathing 100 percent oxygen at normal pressure, here's what happens:

• Fluid accumulates in the lungs.
• Gas flow across the alveoli slows down, meaning that the person has to breathe more to get enough oxygen.
• Chest pains occur during deep breathing.
• The total volume of exchangeable air in the lung decreases by 17 percent.
• Mucus plugs local areas of collapsed alveoli -- a condition called atelectasis. The oxygen trapped in the plugged alveoli gets absorbed into the blood, no gas is left to keep the plugged alveoli inflated, and they collapse. Mucus plugs are normal, but they are cleared by coughing. If alveoli become plugged while breathing air, the nitrogen trapped in the alveoli keeps them inflated.

The astronauts in the Gemini and Apollo programs breathed 100 percent oxygen at reduced pressure for up to two weeks with no problems.

However breathing oxygen at higher than normal pressure is extremely dangerous. In this photo the subject is breathing pure oxygen at 3.5 bars, more than double the amount permitted in actual underwater diving. Of course, the photo is old,and people did more dangerous experiments on humans before WWII, and secondly if he goes into convulsions under close supervision it isn't like going into convulsions while breathing through a regulator.

Quote: Nareed

I recall reading about that. It was in underwater tunnels, right? Underwater tunnel meaning a tunnel that runs under the floor of a river, lake or sea. I wonder how the pressure works in such cases.

The first cases of the bends were when they were building the Brooklyn Bridge. When building the supports the crew had to keep digging dirt from below them and let them sink as they added brick structure on top. They had to keep doing this until they found bedrock. To keep water from leaking into the hole the men were working in they pressurized the space with air. Hundreds of workers ended up with permanent problems from the bends as well as many deaths.

Pure oxygen is always fatal as its the carbonic acid from the CO2 that induces breathing.

Of increasingly greater utility are capnography devices that show not only oxygen levels but also carbon dioxide levels since it can be critical. The brain's instructions to breathe depend on levels of carbonic acid which is CO2 dissolved in the blood.

Dangers from breathing pure oxygen AT NORMAL PRESSURE are from time intervals much longer than those associated with diving.


Okay, SOOPOO. You are the expert on this... who is right?

It would be interesting to know the accident stats on these sort of things, but I bet there aren't any. Or it's lumped in with scuba diving stats or swimming accident stats.

Btw, every time I read about people scuba diving sinkholes and related tunnels, it both sounds like the coolest thing ever and the most terrifying.

Quote: rxwine

It would be interesting to know the accident stats on these sort of things, but I bet there aren't any. Or it's lumped in with scuba diving stats or swimming accident stats.

Well, one tourist town in Florida that had a wave crash over a rocky pier on which there were a dozen fishermen, still lists one of them as 'missing' despite the incident having taken place over a decade ago. So I would assume similar statistics apply to scuba deaths. In foreign resort areas I'm sure no such deaths take place at all.