Why We Use Helitrox on Our PADI Tec 50 Course

Around two years ago, there was a subtle but significant shift in the way many PADI TecRec instructors approach technical diving training.

The PADI TecRec standards still permit training dives to 50 metres using air where appropriate. However, increased emphasis on breathing gas density and the effects of nitrogen narcosis means that many instructors now consider helium to be the better choice for dives approaching 50 metres.

As depth increases, two things happen:

• The density of the breathing gas increases, making it harder to breathe and increasing the risk of carbon dioxide retention.
• The partial pressure of nitrogen increases, leading to progressively greater nitrogen narcosis.

Both factors can impair diver performance at depth. By replacing part of the nitrogen with helium, we reduce both the breathing gas density and the narcotic effect of the breathing mix.

The resulting gas, often referred to as Helitrox or normoxic trimix, allows divers to complete 50-metre dives with significantly lower narcosis while remaining within current PADI TecRec recommendations and accepted technical diving practices.

So why not use helium from the beginning?

The obvious drawback is cost.

Helium is considerably more expensive than air or nitrox and, depending on location, can sometimes be difficult to obtain.

For that reason, we believe a balanced approach offers the best value for most students.

We typically recommend conducting the Tec 40 and Tec 45 courses using air and nitrox, where these gases remain entirely appropriate. Helium is then introduced for the deeper dives of the Tec 50 course, where its benefits become much more significant.

This approach offers several advantages:

• Keeps training costs under control.
• Introduces divers to trimix in a logical progression.
• Reduces gas density during the deepest dives.
• Reduces the effects of nitrogen narcosis.
• Allows students to experience trimix procedures before progressing to more advanced technical diving.

For divers planning to continue beyond Tec 50, this also provides an excellent foundation for future trimix training.

At Professional Diver Training in Khao Lak, Thailand, we believe technical diver education should balance safety, modern best practice and affordability. By introducing helium where it offers the greatest benefit, we can deliver high-quality TecRec training without unnecessarily increasing course costs.