4 Ways to absorb nitrox
PADI Enriched Air Diver
The PADI course is comparable to the TDI course, using similar tables and the Equivalent Air Depth Formula. I took it at Andark Diving's impressive shop/lecture/ pool complex near Southampton. Again like the basic TDI course, this is an entry-level course for mixes from 21 to 40 per cent and does not allow decompression stops. Divers work within no-deco limits to a maximum recreational depth of 40m. For a BSAC-trained diver, a little time needs to be spent with the PADI tables for familiarisation.
The prerequisite is a PADI Advanced Open Water qualification or equivalent, such as BSAC Sports Diver. This is a one-day course, supported by a slick video and well-laid-out course materials, followed by two dives on which the mix must be analysed under supervision and the dive planned. No skills are taught on the dives.
The PADI "crew pack" includes nitrox 32 and 36 tables, which in practice channel PADI-qualified nitrox divers to request these blends in preference to others. The thinking is that other blends require dive planning on EAD tables, which use more rounding and so give fewer decompression advantages.
PADI spends a lot of time, with the help of video, emphasising the maintenance of safe O2 toxicity levels. After the video the real instruction begins: instructor Rob Ciampa took me through the course using a selection of projected slides and working examples. The materials are well-written and well laid-out, and Rob was able to fill in any gaps or misunderstandings. I also had the chance to observe Gas Blender technician Simon Harris mixing and analysing nitrox fills.
The PADI exam consists of 50 multiple-choice questions, of which 75 per cent must be answered correctly. Typically the two course dives are on 36 per cent nitrox to a depth of about 24m at Portland - as no skills are taught I gave these a miss.
Neither the basic TDI nor the PADI courses require specialist equipment, with the exception of tanks, because the maximum permitted bottom mix is 40 per cent and these are no-deco courses. Both offer a quick way to train for nitrox and certification that entitles the holder to buy nitrox around the globe.
Appeared in DIVER - July 1999