General Knowledge - General Science - Discussion

Helium is an inert gas and is not toxic. However breathing pure helium is dangerous because it excludes needed oxygen. Deep sea divers can remain at depth only for controlled periods and must come up slowly and even remain at specified depths to avoid the bends. When ordinary air is used for diving the oxygen in the air is used up by the body but the nitrogen builds up to a new equilibrium state at the higher pressure required at great depths.

One danger that deep sea divers faced was that if they adjusted their air control valves improperly their suit might inflate preventing their hands from reaching the controls to correct the problem. They would then race all the way to the surface like a giant bubble. The excess nitrogen would then come out of tissues and form bubbles (like the fizz in a opened can of soda) in the blood causing the bends and great pain with possible death.

The diver could be placed in a re-compression chamber and pressurized to squeeze the nitrogen bubbles back into the tissues for controlled release during gradual decompression. The expanding nitrogen bubbles in tissues during rapid decompression may also drive away necessary oxygen leading to bone necrosis (bone death). One solution would be to use pure oxygen rather than pure air.

However pure oxygen can be toxic at great concentrations at depth. Therefore oxygen can be mixed with helium to reduce oxygen concentration while eliminating nitrogen. During controlled decompression the helium would also diffuse out of tissues and the lungs more easily than nitrogen avoiding the bends. Use of helium for relatively shallow scuba diving would likely permit longer diving times with less threat of the bends.

Increased pressure in lungs during deep sea diving causes an increased solubility of all gases in the blood. On ascending too quickly, these gases can bubble out of the blood. This is a serious problem with nitrogen as the bubbles can rupture blood vessels causing "The bends".

The He atom is much smaller than the N2 molecule, has a smaller electron cloud and is less polarisable. It therefore is less soluble in blood than nitrogen and is preferred as the above dangers are reduced.

Helium is the substitute for Nitrogen in the deep sea divers their oxygen cylinders contains oxygen with Helium when they were using Nitrogen in the cylinders they found that the divers when they come to the land because of difference in pressure theirs veins get bursted and they used to get bends in their legs and hands.With helium it is not observed as the rate of diffusion of He is greater than nitrogen along with it's non poisonous nature make it suitable to use.

Deep sea divers take oxygen mixed with inert gas say He and adjust the partial pressure of oxygen according to the requirement. Actually, in sea after every 100 feet depth, the divers experiences approximately 3 atm pressure, subnormal air cannot be breathed in depth of sea, moreover, the pressure of n2 increases in depth of sea and it diffuses in the blood.

Heli-air is a form of trimix that is easily blended with helium and air without using pure oxygen. It always has a 21:79 ratio of oxygen to nitrogen; the balance of the mix is helium. Hydreliox is a mixture of oxygen, helium, and hydrogen and is used for dives below 130 metres in commercial diving.

In past time hydrogen is added with nitrogen,they react with each other & forms NH3. Under deep sea, the solubility of the NH3 gas increase with pressure or water head. that NH3 dissolve in blood. when person comes out from sea then concentration of NH3 bubbles produce pain in his body.

Since helium is a inert gas and lighter in weight. So it make oxygen up so that driver can respire properly and if it get mix with blood it have no bad effect and it is also not poisonous gas for human body while respiration.

Helium is just mixed to reduce the solubility of nitrogen into the blood at extreme depth underwater.

Otherwise, it causes bents (pain due to sudden evaporation of nitrogen when diver comes out of water).

Helium is used by sea diver instead of Nitrogen because helium is not react with blood while nitrogen react with blood this cause pain in human body so helium is used because it cause less pain.

Well, oxygen does not dissolve directly into blood under high pressure existing in the deep sea, hence inert gas like helium is mixed with oxygen during deep sea diving. I hope its clear.