Do deep sea divers breath pure oxygen?

Question

if not what do they breath and why?

also wat gas is inside the gas bubbles being exhaled under water through their equipment?
and what happens to that gas??

biology homework.. dont really get it...

Answer 1

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Nope. Pure oxygen is deadly to a diver. It causes what's called oxygen toxicity that can cause a diver to suffer seizures at the very least.
Oxygen content in a breathing mix is depth dependent. The deeper you go, the less oxygen you want in your mix or the less exposure you want to that mix. Over the years from trial and error, dive tables have been developed for the different gas mixes. Basically these tables help a diver figure out mathamatically how to conduct a dive to a certain depth using a certain gas mix for a certain amount of time. They tell you what you can and cannot do. Oxygen isn't the only concern in a breathing mix, since we can't breathe 100% O2. There has to be another gas in that tank(s). It will be nitrogen and maybe even helium, depending on the dive.
The most common gas mix scuba divers use is exactly what you're breathing right now. 21% oxygen, a little over 78% nitrogen and less than 1% other trace gasses like argon. Recreational divers are trained to limit their depth to 130 feet on this mix, but not because of the oxygen content, rather it's because of the narcotic effect that the nitrogen content being inhaled under pressure creates. Well trained and experienced divers can still use this mix to go deeper. 250 feet is possible on it. To go any deeper though, you need to start reducing the oxygen % in that mix ( nitrogen too since it's narcotic and it's effects just get worse) and replace it with a gas that you can breathe and won't cause any narcotic effect or be toxic at depth. The gas of choice is helium since humans can inhale it and it doesn't get narcotic until you're VERY deep. That's why you'll hear some divers on communications gear that sound like they just sucked on a party balloon. This gas blend is commonly called tri mix. It has Oxygen, helium and a little bit of nitrogen. Gas mixes can go down to as low as 6% oxygen content, a little less than 1/3 of what you're used to on the surface but because of the pressures involved, both on the diver and in the diver ( the inhaled gas), you don't suffocate or pass out. If you were in a sealed room at the surface, at 1 atmosphere of pressure ( what's acting on your body right now), you'd be on the floor in a minute breathing this. Why it works this way has to do with a little physics and what's called partial pressures of a gas. Not sure I need to go into that and Dalton's law of partial pressures, but you can easily google that for examples.
There is one other gas mix that divers use commonly called Nitrox. It's kinda like super charged air. Instead of less oxygen as a percentage of volume, it has more. Any diving gas that has more than 21% oxygen by volume can be considered Nitrox or enriched air. You're probably thinking " Wait a minute, isn't oxygen toxic to a diver at depth?" Yep, it is. That's why this mix is used at shallow depths and the higher the oxygen content, the shallower your maximum depth can be. Typically an enriched air mix (nitrox) can be anywhere from 32% to a maximum of 50% oxygen by volume. The 50% mix is used only for things like shallow water decompression stops to help rid the body of absorbed nitrogen a little quicker than normal. The other mixes are actually used for the dive. The advantage using enriched air is that there is a reduced nitrogen content without the expense of helium ( it's costly) which in turn helps limit the amount of nitrogen your body takes on. This gives you a little longer bottom time before you need to either head up or start a decompression schedule.

The exhaled bubbles are carbon dioxide, some oxygen and some nitrogen ( not all of the nitrogen you inhaled though, some is trapped in your body and the reason why divers need to be careful how much nitrogen they absorb) and if you dived trimix, helium. Your exhalations bubble up through the water column until they break surface and mix with the atmosphere.

Answer 2

No-one breathes pure oxygen as it would kill us. The air we breathe contains about 20% oxygen: the rest is mostly nitrogen. deep sea divers breathe a mixture of oxygen and helium: I'm not sure what the proportions are, but I think the oxygen level is quite small (certainly less than 20%). They have to use this mixture as 80% nitrogen at depth causes 'raptures of the deep' (similar to being drunk and making one's thinking muddled). As to bubbles escaping at depth, these will be of the mixture the divers are breathing. It simply rises through the water, expanding as it does so, and mixes with the air at the water surface. If this is biology homework, it will be to do with the various Laws of Pressure.

Answer 3

The answer to the first part of your four part question is No! Divers do not breathe pure oxygen, not at any depth.

Others have covered, more or less, the second part of your question - no need for me to be repetitive.

The content of the exhaled gasses, forming the bubbles under water that you refer to, depends upon the mix used and that is determined by depth and desired duration underwater. It would be accurate at your level for you to say carbon dioxide and unused or residual elements depending upon dive breathe mix employed.

What happens to exhaled gas? Unless you are on a rebreather system, these gas pockets or bubbles will float to surface level unless they meet something on the way up which will interfere with the surface tension around these gasses and cause them to break up.

One small point to note; at sea level the air we all breathe is made up of 21% oxygen, 78% nitrogen, and 1% of other gasses. Although we breathe in this mixture, the average human body at rest actually only uses 5% of the oxygen that it breathes in!!! We exhale 16% of the oxygen that we breathe in - that is why we are able to resusitate other humans when we give mouth to mouth.

Answer 4

What they breathe is compressed air. Yes normal air that every one breathes. This is compressed to 200bar and can last for approx. half an hour depending on the diver. What is exhaled is is also the same, namely carbon dioxide.
Sometimes divers mix gases to different ratios to give themselves longer dive times. This is called 'Ni-trox', which means ( Nitrogen/ Oxygen mixture). The gases exhaled are slightly different.
I hope this helps.

Source(s):

I am a P.A.D.I. Dive instructor

Answer 5

Scubabob covered it very well, and I wanted to added a couple of items:

1. The human body is not used to breathing pure oxygen. Over time, even on the surface, oxygen can become an irritant to your lungs. On the surface this could occur if you breathe pure oxygen for hours upon hours. Most people that you see on oxygen for medical reasons are only breathing a mixture of air and oxygen (much like Nitrox that scubabob described).

2. Some divers do use pure oxygen underwater. These are "technical divers" that have advanced training. The pure oxygen will be used at a very shallow depth (shallower than 20 feet) during the final decompression stops.