Trimix introduces helium into the breathing mixture, alongside oxygen and nitrogen. It is the standard approach to diving beyond the practical limits of air and Nitrox.
Helium is added for three reasons: to reduce narcosis, to manage oxygen exposure at depth, and to reduce gas density so that breathing remains possible without excessive work.
In Australia, Trimix is most relevant at Port Phillip Heads, the Ships' Graveyard, deeper Tasmanian wrecks and the deeper Mount Gambier sinkholes — all places where the interesting terrain continues past where air stops being viable.
Trimix Diver: learning topics
helium's physiological effects and thermal considerations
Discuss how this topic is taught and assessed within the exact programme.
mix selection for a target depth
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multi-gas decompression planning
Discuss how this topic is taught and assessed within the exact programme.
gas density and work of breathing
Discuss how this topic is taught and assessed within the exact programme.
isobaric counterdiffusion awareness
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logistics of sourcing and blending helium
Discuss how this topic is taught and assessed within the exact programme.
Topics recorded in this general course guide, not training instructions or a statement of automatic eligibility. Confirm the programme’s current scope with its agency.
What the course covers
- helium's physiological effects and thermal considerations
- mix selection for a target depth
- multi-gas decompression planning
- gas density and work of breathing
- isobaric counterdiffusion awareness
- logistics of sourcing and blending helium
Gas logistics drive everything
Technical divers often plan entire trips around gas availability. Helium is expensive, supply is variable, and not every centre that advertises technical services actually blends it.
Helium availability should always be treated as time sensitive. A centre that blended Trimix last year may not be doing so this month.
What to verify before committing to a trip
Technical-centre pages must separately verify each of these rather than treating "technical" as a single capability.
Common questions
Where can I get Trimix fills in Australia?
Availability is concentrated in Sydney, Melbourne, Perth and a small number of other centres. It should be confirmed directly and well in advance of any trip.
Why is helium expensive?
Helium is a finite resource with competing industrial and medical demand, and supply is periodically constrained. Prices and availability both fluctuate.
Does Trimix make me colder?
Helium conducts heat more effectively than nitrogen, which is a genuine consideration on long cold-water dives, particularly when used as drysuit inflation gas.