Diving with Nitrox


Why dive with Nitrox? There's several good reasons that make Nitrox a good choice for recreational diving, for those qualified. For a comprehensive article, see benefits of diving with Nitrox, but here are the basics.

  1. Longer Bottom Times:Recreational nitrox (21 - 40% oxygen) contains a lower percentage of nitrogen than air. The reduced percentage of nitrogen in nitrox allows divers to extend their no-decompression limits (or dive time) by reducingnitrogen absorption– the less nitrogen there is in a diver's breathing gas, the slower his nitrogen absorption will be at a given depth. For example, a diver using nitrox with 36% oxygen content (Nitrox 36) may stay up to 40 minutes at 90 feet of sea water, while a diver using air may only stay a maximum of 25 minutes at this depth. (PADI tables)
  2. Shorter Surface Intervals: A diver using nitrox absorbs less nitrogen for a given depth and dive time than a diver using air. This means that the nitrox diver has less nitrogen to off-gas during a surface interval, which can shorten the required surface interval drastically. For example, a diver using Nitrox 32 can repeat a 51 minute dive to 60 feet after 23 minutes, while a diver making a 49 minute dive to 60 feet must wait a minimum of 2 hours 42 minutes to repeat the same dive (PADI tables.)
  3. Longer Repetitive Dive Times: Nitrox becomes especially useful for divers who engage in more than one dive per day. A diver using nitrox will have a longer allowable bottom time on a repetitive dive than a diver using air because the diver using nitrox has absorbed less nitrogen. For example, after a Nitrox 36 dive to 70 feet for 41 minutes, a diver using Nitrox 36 on the repetitive dive can stay at 70 feet for a maximum of 37 minutes if he begins the second dive with between 5 and 9 minutes of surface interval. (Now that’s a fast turnaround time for the second dive!) However, a diver preforming a similar series of dives on air, first dive 70 feet for 40 minutes, may only stay at 70 feet for 4 minutes on his second dive, if it begins with between 7 and 10 minute of surface interval.
  4. Reduced Exhaustion: Many divers claim to feel less exhausted after a dive on nitrox than after a comparable dive on air. By reducing a diver's nitrogen absorption, Ntrox may also reduce a diver's post-dive exhaustion.
  5. Nitrox and Decompression Sickness: The logical conclusion one can draw from diving with the lower exposure to nitrogen experienced by diving with nitrox is that one will have a lower risk of experiencing decompression sickness (DCS). {DCS is caused by the formation of inert gas bubbles (nitrogen) in body tissues and/or the circulatory system.} However, this can’t be conclusively proven by accident statistics. Primarily this is because the incident rate of DCS for all recreational dives is so low that when separated into air and nitrox dives the difference incident rates is about .001%
  6. Oxygen Toxicity: Like most good things in life (ice cream, chocolate, etc.) too much of a good thing can be harmful. This holds true for oxygen too. For this reason there are limits to the amount of oxygen used in recreational nitrox diving and limits to the depths that we dive various gas mixtures. For added safety each diver also analyzes the gas mixture in their tank before diving with it.
  7. Shorter Decompression: Technical divers use nitrox to reduce decompression requirements. If nitrox is used throughout the dive, the diver may require shorter or fewer decompression stops. If nitrox is used as a decompression gas (the diver only breathes nitrox during the decompression stops), the decompression stops will be shorter.

Certification Requirements

Up until a few years ago most dive agencies required a number of dives to be made as part of the nitrox certification course. This is no longer the case and for good reason. The physical aspects of nitrox diving are not any different than diving on air. The differences are in dive planning and are mostly related to understanding oxygen & depth limits. The requirements for certification are completion of an academic course (one that is very well suited to online eLearning) and completion of a short practical session. During the practical session the instructor ensures that you know how to plan your dives, use your computer (if you have one, if not dives can be made using nitrox tables) and guides you through analyzing tanks containing various nitrox blends.

Nitrox Training

The Special “club” Deal: BBD $200 for online training course, practical session, Nitrox Diver certification and certification card from the (NASE) National Academy of Scuba Educators. (See link below) http://www.naseworldwide.org/index.da

Availability of Nitrox 

Nitrox is available on island and Club members can often get a preferential rate on club dives. Contact to the Dive Officer or dive organiser to see if nitrox will be available.