Who needs to take four nitrox courses I did - for research purposes, but I reckoned it could only stand me in good stead in the future. As a BSAC Sports Diver, I came to the subject fresh. I knew that converts to nitrox diving wouldnt dive any other way given the choice, and I understood in outline the claims made for it.
Air, I knew, was a form of nitrox - nitrox 21, containing some 78 per cent nitrogen, 21 per cent oxygen and other gases. The nitrogen component is the part that could cause decompression sickness when breathed under pressure and absorbed into the tissues, if you stayed under water too long or failed to make decompression stops.
Reduce the amount of nitrogen by increasing the oxygen in the mix to varying degrees, and you could enjoy longer bottom times, or build in an extra safety margin by continuing to behave as if you were diving on air.
You could also use the oxygen-rich mix on a decompression stop to eliminate nitrogen from the body faster. However, by increasing the amount of oxygen in the mix, you increase its partial pressure, so depending on the mix could encounter oxygen toxicity problems at depths shallower than the 60m threshold for diving on air. Hence the need to understand the maths - I knew all that, but it was just the start.
  • TDI Nitrox Diver
  • PADI Enriched Air Diver
  • BSAC Advanced Nitrox Diver
  • IANTD Advanced Nitrox Diver

TDI (MIDDLE EAST) NITROX DIVER is open to Sports Divers/Advanced Open Water Divers. Stephen Lees course was held on live-aboard mv Nouran, out of Hurghada, Egypt, organised by Diving World (0171 407 0019). Cost of week from £770 including flight, transfers, food, tanks/air and weights. Flights courtesy of Caledonian (01293 536 321). The course cost £90, including two non-mandatory nitrox dives.
TDI ADVANCED NITROX DIVER requires TDI Nitrox Diver or the equivalent qualification and takes two days. It covers deco diving, includes two assessment dives and costs £150-175. Contact Dave Crockford at DDRC on 01752 209999. PADI ENRICHED AIR DIVER PADI offers only a basic nitrox. It costs £150, with two dives. The one featured was run by Andark Diving, Lower Swanwick, Southampton (01489 581755).
BSAC NITROX DIVER is open to Sports Divers or equivalent with at least 20 dives since qualifying. It teaches use of nitrox 32 and 36 with no-deco-stop dives, and is a one-day paper/ classroom qualification with no assessment dives. Cost from £25-70 depending on whether it is done at a branch or via the coaching scheme.
BSAC ADVANCED NITROX DIVER, described in the feature, costs from 55-150 depending on training environment. A school or coaching scheme is typically £130-150 to non-BSAC members, and a branch scheme £55-70, including dives. Entry level is as for BSAC Nitrox Diver. The course occupies a longer day in the classroom and two assessment dives, but basic and advanced courses can be combined. Call BSAC on 0151 350 6200. Diving facilities were provided by Breakwater Diving Centre/ AquaSport Hotel, Portland (01305 860269).
IANTD NITROX DIVER COURSE is open to a PADI Open Water diver or BSAC Ocean/Club Diver with 10 dives. One day in the classroom plus two dives costs from £140.
IANTD ADVANCED NITROX DIVER is generally open to experienced Advanced Open Water/Sports Divers, though this is at the instructors discretion. The £175 cost covers dives and hire of equipment. Stephen Lees course was organised by Portland Dive Centre, which also provides accommodation (01305 820870).