Technical training

Trimix Diver

Adding helium to manage narcosis, oxygen exposure and gas density at depth.

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.

Technical wreck diving, represented by an AI-generated editorial image.

Track	Technical
Prerequisites	Decompression Procedures; Advanced Nitrox; Substantial logged technical experience
Agency equivalents	TDI: Trimix Diver · PADI: Tec Trimix · IANTD: Trimix Diver · RAID: Trimix

What it teaches

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.

Trimix courses offered and at what level
helium availability and current supply
oxygen for decompression gases
custom blending versus fixed mixes
suitable cylinders and stage hire
analyser availability

Where this qualification matters in Australia

Sites where holding this certification genuinely changes what you can do — not a list of everywhere it is accepted.

Ships' GraveyardNumerous vessels deliberately scuttled outside Port Phillip Bay across a wide depth range.Port Phillip Heads WallsWalls starting at 12 metres and continuing beyond 90 — the terrain behind Victoria's technical culture.SS NordA steamer lost in 1915, lying around 42 metres off the Tasman Peninsula.Piccaninnie PondsA karst spring of extraordinary clarity, with the Cathedral chamber and a chasm beyond 100 metres.Lonsdale WallVictoria's signature wall — sponge-covered, vertical, and continuing well past recreational depth.

Natural next steps

Courses that build directly on this one.

Closed Circuit Rebreather DiverRecycling breathing gas to extend duration, reduce bubbles and optimise oxygen exposure.Cave DiverFull overhead penetration diving, where direct ascent is not available at any point.

Courses that lead here

Deep DiverExtending recreational limits to 40 metres, with the gas planning and narcosis awareness that requires.Cave DiverFull overhead penetration diving, where direct ascent is not available at any point.Advanced NitroxHigh-oxygen decompression gases and oxygen-clean equipment — not ordinary recreational Nitrox.Decompression ProceduresPlanning and executing dives with a mandatory decompression obligation.Closed Circuit Rebreather DiverRecycling breathing gas to extend duration, reduce bubbles and optimise oxygen exposure.

Agency versions of this course

The same qualification under different names. All are mutually recognised by operators.

TDITaught as “Trimix Diver”.PADITaught as “Tec Trimix”.IANTDTaught as “Trimix Diver”.RAIDTaught as “Trimix”.

Centres documented as offering this level of training

Businesses where the relevant capability is verified or advertised. Always confirm the specific course directly.

Dive Dive DiveA long-standing Brisbane business associated with technical training alongside recreational courses, retail and servicing. Technical capability should be audited service by service rather than assumed.Dive Centre ManlyA Northern Beaches operation with a long-standing presence at Shelly Beach, offering recreational training, boat diving and technical pathways.Frog Dive SydneyA long-established Sydney business associated with recreational and technical training alongside retail and workshop services.Abyss Scuba DivingA Sydney operation associated with training across recreational and technical levels, boat diving and equipment services.Dive Centre BondiAn Eastern Suburbs operation providing recreational training, local diving and technical pathways.Academy of ScubaA Melbourne training business offering recreational courses with technical pathways.Diveline Scuba CentreA Victorian business associated with technical training and gas support alongside recreational courses.AquabilityA Victorian operation associated with technical diving training. Exact agency, course levels and gas support require verification.Bay City ScubaA Victorian business associated with recreational and technical training alongside equipment and gas services.Ocean DiversA Victorian operation associated with recreational and technical training and access to Port Phillip diving.Snorkel & Dive Safari AltonaA Melbourne retail and training business, listed among Victorian operations associated with technical services.All About ScubaA Victorian training operation listed among those associated with technical diving. Capability requires verification.

Frequently asked 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.