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Given that a basic technical diving principle is safety, it is puzzling that even nowadays, acceptance of trimix ( use of helium ) diving in some circles is still reluctant. We are diving deep or under physical ceilings such as wrecks or caves where human mistakes and equipment failures would be costly. Our safety comes from the diver possessing an adequate skill set for the environment, from back up equipment, and critically, from proper gas choice for the depth at which he or she is operating. Diving with trimix clearly fulfils this final point.
Twenty years and more ago, trimix diving was only really considered for dives that just couldn’t be done on air, and even then, used sparingly. This was hardly a surprise given the relative lack of knowledge and testing of trimix in the technical community. Now we see a much more liberal use of the gas, throughout the depth range to 40m and even shallower. So what’s the story?
Historical Background
Early testing of trimix as a breathable diving gas goes back to US Navy work in the 1920’s. Cost prohibited much research, but by 1937 Max Nohl had managed to make a successful 127m dive, and in 1939 the US Navy used trimix in the spectacular salvage of the submarine USS Squalus that sank herself in sea trials ( interestingly the actual rescue of the trapped crew was done on air as there was no time to bring mixed gas to the scene, but the actual salvage was done using trimix ).
The Terrible Hours : The Greatest Submarine Rescue In History, by Peter Maas, is a great account.
In the 1960’s the offshore oil industry began using heliox, in 1970, technical diving pioneer Hal Watts made a 126m recovery dive, and in 1987, cave diving legend Sheck Exley became the first to instruct divers in the use of trimix for cave diving in Florida. IANTD ( International Association of Nitrox and Technical Divers ) began teaching trimix courses in 1991, then for diving in the 60-90m range, but now has programs that provide for it’s use from just 30m on down.
How this gas works
- With Trimix helium is used to replace some of the nitrogen in our gas, and therefore limit our nitrogen narcosis on deep dives – helium is not narcotic at all.
- For deeper dives it also replaces some of the oxygen, allowing a partial pressure of O2 that is not a threat to the diver.
- Diving with this gas also greatly reduces gas density, and therefore effort of breathing and the deeper divers tendency to retain carbon dioxide. This helps because carbon dioxide is not only extremely narcotic, it makes us more susceptible to both oxygen toxicity, and to decompression sickness.
Essentially, Helium is an easy to breathe, completely inert gas that reduces the effect of all the other gas problems in a dive, without causing any of its own.
Some problems.
These are hard to find… Trimix in the past was blamed for descent problems such as High Pressure Neurological Syndrome. But this is irrelevant unless you descend quickly to 200m or so and has now been dropped from the curriculum. It was purported that breathing trimix makes you colder. Practical experience simply does not bear this out. The only thermal concern is it’s not a good insulator, therefore no good as a drysuit gas.
Decompression used to be sited as a concern or complication, but again this turns out untrue. Helium passes easily in and out of the tissues, is not critically unforgiving of ascent rate as some would have us believe, and only marginally increases the need for deeper stops. Post dive fatigue is drastically reduced compared to air.
Tech Asia provides IANTD certifications all the way through the trimix levels and on to Instructor. DSAT Tec Trimix courses are also available, and daily trimix
dives run from the shop, plus we organise national and international trips.
What can we show you ?
Marine life, and lots of it. Asia Divers and our
Tech Diving Institute is situated smack in the
middle of a biodiversity hotspot, the renowned Verde
Island passage, and our local waters form a
protected marine reserve, teeming with life, big and
small.
Wreck diving too. World Wars and weather have put countless ship wrecks on the seabed all over the country, some quite shallow, some very deep. The Philippines offers it all. Check out our articles for an idea. Articles.
This short video below will give you some idea as to why so many people travel to the Philippines for diving vacations.
A recent survey found that once a diver had visited the Philippines, he or she will return on average ten times.
Whatever kind of diving you want to do, we have the
diving for you here. |
