Advanced nitrox

Published by rdevanney on

advanced nitrox

Advanced Nitrox


The next step after completing the Intro to Tech or Sidemount course is to learn more about dive planning. Following a dive plan is essential for decompression diving. Advanced nitrox is designed with this in mind. Decompression divers also use higher mixtures of oxygen. Advanced nitrox introduces the equipment and procedures required to do this safely. Setting up and handling a decompression cylinder, and learning a safe and effective gas-switching process is fundamental to the course.


Dive Agency Certifications

Most of the prominent dive agencies have their version of advanced nitrox, except PADI. Tec 45 is perhaps the closest equivalent. I’ll focus on the last two agencies that I was teaching under, TDI’s advanced nitrox, and Raid’s Deco 40. TDI advanced nitrox doesn’t allow decompression diving, but mixtures of nitrox greater than 40% are used. Dives are permitted down to 40m (130ft). The point of advanced nitrox is to lay the foundations for the next course; decompression procedures.


Certification for the Raid Deco 40 course is down to 40m (130ft), and a limit of 10 minutes of decompression is allowed. Deco 40 is a strange beast. The course is aimed squarely at recreational divers- Raid created this course to act as a bridge between recreational and technical diving. The course allows divers to continue using a single cylinder with an additional separate cylinder.


It seems more sensible to encourage divers to learn advanced nitrox or deco 40 with equipment that will be used in every other technical dive course. Sidemount is an ideal configuration for recreational divers who don’t like the idea of using a twinset.


One fantastic thing about the Deco 40 course is the optional use of Trimix. This is a great way to show the benefits of using helium.


Course length

Advanced nitrox/Deco 40 requires 6 dives minimum and takes 4 days to complete. As with any tech course, theory, land practice, and open-water dives are required. A pool session is also required on the Deco 40 course.


Although I’m qualified to teach technical diving with TDI, SSI XR, PADI TecRec, IANTD, and Raid, it doesn’t matter which course is run. Students learn my way of tech diving at that level. Physiology doesn’t change between agencies, neither does deco theory or how you handle an out-of-gas emergency for example.


With each course, the rules that the instructor needs to follow during the course are slightly different. This may include maximum depth for each dive, and some skills must be practised on specific dives with Raid, but not with TDI. The difference in qualification for the student is whether they can undertake limited accelerated decompression- not with TDI.


The theory involves more in-depth dive planning, which includes using nitrox mixtures up to 100% O2. Decompression theory and diving physiology are also covered in more detail.


Required Skills

Skills aquired during the intro to tech course are recapped, and additional skills are introduced and practised, such as:


  • Gas switching
  • Free-flowing deco reg
  • Out of deco gas
  • Staging and retrieving the deco cylinder
  • Towing a diver with an extra cylinder- underwater and on the surface
  • Ascent practice, including gas switching
  • Toxing diver rescue
  • Wing failure
  • LPI failure


Students plan dives using software and follow it during the dive. Advanced nitrox provides a solid base for the next level of diving- decompression diving.

The minimum prerequisites for starting this course include:

  • 18 years old
  • Advanced OW diver
  • Nitrox diver

The minimum prerequisites for starting this course include:

  • 18 years old with parental consent
  • Advanced OW diver
  • Nitrox diver

Header image photo credit: James Emery Photo

Decompression diving

Courses overview