Quote:
| Originally Posted by [b Quote[/b] (JohnDuncan @ Mar. 11 2004,11:21)]I am trying to find out what are the advantages of using Heli-air. I know that it is sometimes known as "poor mans trimix" but are there advantages and disadvantages. The END for the normoxic mixes are still quite high e.g. 16/24/60 at 60m is 43m END and at 70m it is 51m END |
<font color='#8D38C9'>I have used it - particularly for line laying and surveying in caves below 40 m. I prefer at least 30% He or more otherwise there is not much narcosis benefit but even a little can help.
The advantages are:
0. I don't have a trimix (or even nitrox) ticket.
1. Its cheap - I use Helium at work...
2. Easy to make.
3. Easy to analyse (and re-analyse if you top it off with air).
The disadvantage is that anything pokier that Helair 17:20 is potentially hypoxic on the surface. However I've got travel/deco gas to breathe and even if I did dive from the surface on a light O2 mix then I'm quickly going to be at a depth where the ppO2 has risen. When you get to around 60-70 m you need a mix that would be hypoxic on the surface anyway.
10:50 is a popular diluent.
Duncan