When BSAC created its own Nitrox Training programme in 1995 the authors of these manuals and courses recommended a maximum PO2 (Partial Pressure of Oxygen) of 1.4 bar. This was decided upon from information known about the safe levels of oxygen to ensure the diver is kept well away from oxygen toxicity. Now nearly 20 years on it can be seen that this recommendation was a good one as there are no reports of oxygen toxicity problems in BSAC recreational or technical diving.
Partial pressure of oxygen
The PO2 of 1.4 bar is also recommended by other training agencies including the other technical agencies. The American training agencies start with a maximum PO2 of 1.6 bar and recommend reducing it by set levels when diving in more extreme conditions such as cold water, long decompression stops and diver's higher work rate. In this way their recommendations could end up below that of 1.4 bar. These training agencies have recognised the increased risk of a problem in these more difficult conditions. The BSAC took the initial view that our divers were being trained and diving in northern European waters and that they face these harsher conditions most of the time in comparison to those diving in the waters of Florida.
The other technical agencies also reduce the maximum PO2 recommendation the more advanced, or more technical, the diving qualification becomes. For example, once Trimix is used, all agencies recommend a maximum PO2 of 1.4 bar for the bottom gas.
Use of Nitrox 80 for decompression
When the BSAC Extended Range Diver course was released, another recommendation was to use a maximum of Nitrox 80 as a decompression gas. The reason for this recommendation was to link with the BSAC PO2 recommendation of 1.4 bar since Nitrox 80 can be used at 6 metres, where most decompression stops are carried out when using BSAC 88 tables.
The recommendation for using Nitrox 80 as a decompression gas was not in opposition to using 100% oxygen but more to take advantage of the increased safety of using a weaker Nitrox mix as a decompression gas. This weaker mix of Nitrox 80 can be used safely at deeper depths, which allows for a faster and therefore shorter decompression schedule. If comparative schedules are run on any decompression software the enhancement of the off gassing phase will be clearly identified.
BSAC statement on the use and purchase of 100% oxygen
BSAC now endorses the use of 100% oxygen for suitably qualified members. For conditions of use see: BSAC Technical Safe Diving. The advice on maximum PO2 exposure should be considered when using 100% oxygen.
BSAC courses, which qualify our members to use and purchase 100%, oxygen are:
- BSAC Extended Range Diver
- BSAC Inspiration CCR
To purchase 100% oxygen evidence of qualification is required. Historically BSAC ERD divers have been restricted to 80% oxygen. This statement can be used as evidence, with an ERD qualification, that our members can purchase 100% oxygen.
