Trimix (breathing gas)

Trimix is a special breathing gas mixture of oxygen, nitrogen and helium, which is used in technical diving to reach greater depths. By the addition of helium in the respiratory gas of O2 and N2 partial pressure is adjusted to acceptable levels. The negative effects of oxygen and nitrogen ( nitrogen narcosis, oxygen poisoning of the CNS and decompression sickness ) are thereby reduced. In general, the term is used when the oxygen content is 21 % or less. At an oxygen content> 21%, the mixture is called Triox.

By adding a helium Sauerstoff-/Stickstoffnarkose is largely suppressed in order to be able to visit hereby depths below the usual sport divers limit of 40 meters. Another advantage is the much lower density compared to air of the gas mixture. This results in a lower work of breathing regulator and a reduction in risk of hypercapnia. As a negative side effect of the High Pressure Nervous Syndrome ( HPNS ) can occur, which is caused by helium at depths from about 130 meters in conjunction with high descent speeds.

Tests of the journal Diving (issue November 2009) have shown that when using trimix the temperature in the first stage of the regulator can be up to about 25 ° C. higher than when using compressed air. This could reduce the risk of freezing of the pressure regulator and the regulator, which often causes a malfunction of the above-mentioned parts in the form of uncontrolled escape of breathing gas.

Designation and examples

Trimix mixtures are named according to the proportions of oxygen and helium. The designation of the mixture as formed as follows: Tx oxygen / helium content. So contains a mixture called Tx21/35 example, 21% O2 and 35 % He. The rest of 44% is nitrogen.

Common Trimixmischungen

The mixtures mentioned have in common that the oxygen partial pressure is on the target depth below 1.3 bar. The equivalent narcosis depth ( END - Equivalent Narcotic Depth) is shallower than 30 m, respectively. In the mixtures, the oxygen content is below 18%, it is noted that they are not breathable without the risk of hypoxia at the surface.

Special cases and alternatives

Heliair

Speaking of trimix, it is felt each other a free ratio of the proportions of helium, oxygen and nitrogen. A special case is the so-called Heliair, wherein the breathing air is mixed with a proportion of helium. Advantage is the much simpler and thus favorable production. Disadvantage is that the oxygen partial pressure of the final mixture decreases. Thus it is no longer usable may from the water surface to dive when the partial pressure of oxygen PO2 is less than 0.16 bar.

Professional divers and greater depths

Professional divers are insured in Switzerland with SUVA and may only dive with Heliox, a helium -oxygen mixture without nitrogen. Larger depths can also mixtures such as Hydrox that of hydrogen (Latin Hydrogenium ) and oxygen, as well as hydreliox - hydrogen, helium, and oxygen - can be achieved. With Hydrox divers could reach depths of 700 m.