Mix It Up

The final part of my marathon training block was the 2-day Oxygen Technician and Gas Blenders course. This started in the classroom, discussing Oxygen handling techniques and enriched breathing mixture (i.e. Nitrox or EANx).

We were introduced to the excellent CCR Mixer app from Mikael Fridholm. This allows you to specify your target mix and cylinder pressure along with your starting position whether that be an empty cylinder, or a partially filled cylinder with a different Nitrox mix. The app then tells you if you need to drain the cylinder and provides instructions for creating your target mix using the following methods:

  • Partial pressure blending
  • Inline blending
  • From a bank

Before moving to the workshop I calculated the steps for filling a cylinder with EANx 32 at 200 bar from a cylinder with EANx 40 at 50 bar. The results in the app are shown below:

I was using the partial pressure method so I added the required 15.8 bar of Oxygen, then air (which was actually stored in a bank) to bring the final pressure to 200 bar. I left the cylinder to cool, rechecked the pressure, topped up with air and then analysed the mix to confirm it was within 1% of the target.

On day 2 we moved on to breathing mixtures containing Helium; Heli-air, Heliox and Tri-mix. We started with an investigation of Helium, where it comes from and it’s physical properties before moving on to issues to consider when using Tri-mix. We studied the Hypoxic Ceiling which is the depth (for a given mixture) above which hypoxia and unconsciousness is likely to occur due to the low percentage of Oxygen in the mix. We learnt about analysing Tri-mix blend using both an O2 analyser and a Tri-mix-analyser.

Finally we moved on to the maintenance and cleaning Oxygen equipment. This involved the changes required in the workshop, the additional tools needs and the enhanced processes need to keep all necessary equipment in an Oxygen Clean status.

I’m pleased to have scored 90% over this course. I feel proud to have qualified as an ASSET Oxygen Technician and as an EN ISO 13239:2012 Level 2 gas blender.