Heliair
Encyclopedia
Heliair is a breathing gas
consisting of mixture of oxygen
, nitrogen
and helium
and is often used during the deep phase of dives carried out using technical diving
techniques. This term, first used by Sheck Exley
, is mostly used by Technical Diving International
.
It is easily blended
from helium and air and so has a fixed 21:79 ratio of oxygen to nitrogen with the balance consisting of a variable amount of helium. It is sometimes referred to as "poor man's trimix", because it is much easier to blend than trimix blends with variable oxygen content, since all that is required is to insert the requisite partial pressure
of helium, and then top up with air from a conventional compressor. The more complicated (and dangerous) step of adding pure oxygen at pressure required to blend trimix is absent when blending heliair.
Breathing gas
Breathing gas is a mixture of gaseous chemical elements and compounds used for respiration.Air is the most common and only natural breathing gas...
consisting of mixture of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
, nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
and helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
and is often used during the deep phase of dives carried out using technical diving
Technical diving
Technical diving is a form of scuba diving that exceeds the scope of recreational diving...
techniques. This term, first used by Sheck Exley
Sheck Exley
-Biography:Exley is widely regarded as one of the pioneers of cave diving, writing two major books on the subject: Basic Cave Diving: A Blueprint for Survival and Caverns Measureless to Man published by Cave Books, , and establishing many of the basic safety procedures used in cave and overhead...
, is mostly used by Technical Diving International
Technical Diving International
Technical Diving International is the largest technical diving certification agency in the world. As one of the first agencies to provide training in mixed gas diving and rebreathers, TDI is seen as an innovator of new diving techniques and programs which previously were not available to the...
.
It is easily blended
Gas blending
Gas blending or gas mixing is the filling of diving cylinders with non-air breathing gases such as nitrox, trimix and heliox.Filling cylinders with a mixture of gases has dangers for both the filler and the diver. During filling there is a risk of fire due to use of oxygen and a risk of explosion...
from helium and air and so has a fixed 21:79 ratio of oxygen to nitrogen with the balance consisting of a variable amount of helium. It is sometimes referred to as "poor man's trimix", because it is much easier to blend than trimix blends with variable oxygen content, since all that is required is to insert the requisite partial pressure
Partial pressure
In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. The total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture....
of helium, and then top up with air from a conventional compressor. The more complicated (and dangerous) step of adding pure oxygen at pressure required to blend trimix is absent when blending heliair.