4 Ways to absorb nitrox
IANTD Advanced Nitrox Diver
With three other courses and a good basic understanding behind me, I expected the IANTD Advanced Nitrox Diver course to be easy. I was wrong. The manual contained 132 pages of condensed information, with a lot more detail than the other courses.
This course has a maximum bottom mix of 40 per cent and maximum deco mix of 50 per cent, but uses the EAD concept/residual nitrox times and the IANTD Buhlmann-based tables. Much reliance is placed on calculations to three decimal points, taking maximum advantage of no-stop and minimum deco times.
The principles are the same, but the detail in the IANTD teaching was far more complex. Theory instruction was by laptop and worked example, but it seemed that the laptop teaching aids had been prepared at a different time to the course manual, making it hard to follow the two in tandem.
And my instructor Steve Collins was always ready to throw in a corker of a question to see if I had understood the topic and the practical implications!
He made it clear that even with a limited decompression programme, deco is the hardest part of nitrox, and should always be a planned event. We spent much time discussing how and when the SMB would be deployed, with the deco mix turned on in advance so there would be less to think about on the stop itself.
The exam was infinitely more difficult than any of the others, even though the information was fresh in my mind. There were hardly any "multiple-guess" questions; instead, I was faced with 42 probing problems designed to root out any imperfect understanding of the subject.
There was no way I could achieve the 80 per cent pass mark by guessing, as was possible with some of the other courses. Despite being an open-book exam, the IANTD manual is so detailed that it was hard to find a quick answer without reading and understanding the whole chapter. This might just be intentional!
IANTD stresses a diver's physical and mental preparation, as well as breathing techniques. This is a course not just for nitrox but for any diver who wishes to improve every aspect of his or her diving.
Steve was thorough, methodical and patient in the classroom, but if I had expected an easy ride on the assessment dives, I was mistaken. We dived the Countess of Erne just outside Portland Harbour again, using a bottom mix of 32 per cent and a 50 per cent deco mix.
The aim was skill revision, deco buoyancy and deployment of a delayed surface marker buoy. Nothing seemed to go right as I again struggled with current, DSMB, unfamiliar kit, absence of visibility and lack of hands.
Steve told me in no uncertain terms to reconfigure my kit for the next dive, on the Benny. This time I had everything tight and in the right place, managing to crack the DSMB, turn on the deco mix, change regulators, control the DSMB and maintain buoyancy, all in more or less the right order. Job done, assessment passed: IANTD Advanced Nitrox Diver.
I was surprised how challenging this course was. It stretched my mental and physical skills, was the most thought-provoking course and the one most likely to make me a better diver, partly due to Portland Diving, partly to Steve.
But each course has plenty to offer. The TDI basic and PADI Enriched Air Diver courses were the easiest ways to obtain a qualification and be able to buy a nitrox fill up to 40 per cent for no-decompression diving. These courses would be adequate for recreational-warm-water, good-visibility divers who don't want to be bogged down by technicalities or have to buy a pony and oxygen-cleaned regulator.
If you are a more self-reliant diver not averse to decompression and diving in the UK, frequently using SMBs, prepared to buy the equipment and practice the skills needed to use it, then do an advanced course. If you like calculation-free diving, the BSAC course and materials are easy to use. If you want all of the above and more, go for the IANTD option and surface with much more than a nitrox qualification.
Manuals don't tell you about dodgy nitrox filler station/analysis tricks but a worldy-wise instructor hopefully will He could also tell you that a diver can still get bent diving within tables, whichever ones are used, if he is having a bad day.
But the more you know and the more you practice, the fewer bad days you will have. As one training agency puts it: "To air is human, to nitrox divine".
Appeared in DIVER - July 1999