Technical diving

Trimix

Helium in the breathing mix — and the gas logistics that determine whether a trip is possible.

Trimix introduces helium into the breathing mixture to manage narcosis, oxygen exposure and gas density at depth.

For Australian divers it 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 divers often plan entire trips around gas logistics, because helium is expensive, supply fluctuates and not every centre advertising technical services actually blends it.

Why helium is added

Helium is not narcotic at the depths recreational and technical divers reach, it allows oxygen fraction to be reduced for deep exposure, and it is far less dense than nitrogen so breathing work stays manageable.

Gas density in particular is under-appreciated: dense gas at depth increases carbon dioxide retention, which is implicated in a range of diving incidents.

Verify these separately

A centre may teach Trimix without blending it, or blend it without teaching it. Treat each as its own question.

Trimix courses and at what level
helium availability and current supply
oxygen for decompression gases
custom blending versus fixed mixes
suitable cylinders and stage hire
booster availability for high-pressure fills

Helium availability is time sensitive

Helium is a finite resource with competing industrial and medical demand, and global supply has been constrained repeatedly.

A centre that blended Trimix last year may not be doing so this month. Always confirm close to the trip rather than relying on a website.

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

Related training

Trimix DiverAdding helium to manage narcosis, oxygen exposure and gas density at depth.Decompression ProceduresPlanning and executing dives with a mandatory decompression obligation.Advanced NitroxHigh-oxygen decompression gases and oxygen-clean equipment — not ordinary recreational Nitrox.

Where this applies in Australia

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.Lonsdale WallVictoria's signature wall — sponge-covered, vertical, and continuing well past recreational depth.

Centres where this capability is documented

Documented does not mean verified in every detail — confirm the specific service directly.

Dive Centre ManlyA Northern Beaches operation with a long-standing presence at Shelly Beach, offering recreational training, boat diving and technical pathways.The Scuba DoctorA Victorian equipment and service business with an extensive retail presence, located to serve both Melbourne and Mornington Peninsula divers.Perth ScubaOne of the most fully documented operations in Western Australia, covering recreational, professional, technical and freediving training alongside substantial equipment facilities.Dolphin Scuba DivingA Perth business providing training, equipment and service support.Tasmania Tech and Dive CentreThe Tasmanian operation most clearly associated with technical diving services, spanning recreational and technical training with technical gas support.

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. Confirm directly and well in advance.

Does helium make me colder?

Helium conducts heat more effectively than nitrogen, which is a genuine consideration on long cold-water dives and for drysuit inflation gas choice.