Specialties · Enriched Air Nitrox · SSI
There is one specialty we recommend with almost every course, regardless of a diver's level: the SSI Enriched Air Nitrox specialty. It is the most popular diving specialty in the world, and for good reason. With a renewed SSI programme (launched this week), there has never been a better moment to tell you more about it.
What is nitrox, exactly?
Regular compressed air consists of approximately 21% oxygen and 78% nitrogen. Nitrox (also known as Enriched Air or EANx) is simply a gas mixture with a higher oxygen percentage. The most commonly used blends are EANx32 (32% oxygen) and EANx36 (36% oxygen). With the SSI Enriched Air Nitrox specialty, you are certified to dive with blends up to 40%.
Less nitrogen in your breathing gas means less nitrogen building up in your body during the dive. And that comes with a number of practical benefits.
The benefits of nitrox
- Longer no-decompression limits: The best-known benefit: nitrox gives you more time at depth before reaching your no-decompression limit (NDL). At 20 metres on compressed air, your NDL is around 45 minutes. With EANx32, that extends to approximately 70 minutes; well over a third more. At 25 metres the effect is even more pronounced, going from around 25 to 40 minutes.
- Less nitrogen build-up. Breathing less nitrogen means less nitrogen in your tissues. This is particularly useful on multi-dive days, where residual nitrogen from a previous dive reduces your NDLs. But even on a single dive, you lower your nitrogen absorption and with it the risk of decompression sickness.
- Shorter surface intervals. Because you absorb less nitrogen, you need less time to off-gas between dives. On a day with two or more dives, you will notice this directly: you can get back in the water sooner.
- More conservative diving. Many divers use nitrox not to dive longer, but to make the same dive more conservatively. You have more margin and dive more comfortably within your limits.
- Less fatigue. This is a benefit that is difficult to measure precisely, but is widely reported: divers who use nitrox tend to feel less tired after a dive. The exact reason and whether it holds up objectively is hard to pin down, but reduced nitrogen absorption likely plays a role. Anyone who has had a long day of diving on compressed air will recognise that vague post-dive tiredness. With nitrox, many divers find it is noticeably less.
Some fun facts
- Nitrox has existed since the 1970s, but was for a long time used only by military and technical divers. PADI introduced it as a recreational specialty in 1985.
- A diver on EANx32 at 20 metres absorbs around 35% less nitrogen than someone breathing compressed air at the same depth.
- The most common term for nitrox is "Enriched Air". The word nitrox itself sounds alarming to non-divers, whereas in practice it is actually a more conservative gas than standard air.
- On many liveaboards worldwide, nitrox is included as standard or available for a small surcharge.
- On Bonaire (Diver's Paradise), nitrox fills cost the same as air fills, simply because the extra safety benefit is considered a given.
Common misconceptions debunked
"Nitrox is for deep dives" This is the most persistent myth, and the truth is the exact opposite. Because of the higher oxygen percentage, nitrox actually has a maximum operating depth (MOD) that is shallower than compressed air. EANx32 has an MOD of 33 metres; EANx36 of 28 metres. Diving deeper than your MOD on nitrox carries a risk of oxygen toxicity, a serious condition you want to avoid. In the Netherlands this is rarely a practical concern, since most dive sites in the Grevelingen and the Oosterschelde fall well within those limits.
"Nitrox is expensive" Nitrox can carry a small surcharge compared to a standard air fill, but that is by no means universal. At many dive sites and liveaboards the price is the same or it is included as standard. And even where a small surcharge applies: weigh that against the benefits of extra bottom time, shorter surface intervals and less fatigue.
"Nitrox means I can dive longer" Partly true, but with an important nuance. Nitrox gives you a longer NDL, but it does not determine how long your cylinder lasts. Your air consumption does not change because you are on nitrox. When your cylinder is empty, your dive is over. The benefit lies mainly in repetitive diving and in the extra margin you carry throughout the dive.
"Nitrox eliminates the risk of decompression sickness" Not at all. Nitrox reduces nitrogen absorption, but it does not make you immune to decompression sickness. You still need to set your dive computer to the correct gas mix, monitor your NDLs and complete your safety stop.
"I don't need a course to use nitrox" Technically, you cannot simply pick up a nitrox cylinder without certification. You need to know how to analyse the cylinder, calculate your MOD and configure your dive computer correctly. It sounds more complicated than it is; it is exactly what you learn during the specialty.
What do you learn during the SSI Enriched Air Nitrox specialty?
The course consists mainly of theory, which makes it easy to combine with practical courses such as the AOWD or other specialties. You will learn:
- How nitrox works and what it does to your body physically
- How to analyse a cylinder and verify the oxygen percentage
- How to calculate your maximum operating depth (MOD)
- How to configure your dive computer for nitrox
- How to manage and track your oxygen exposure
- How to safely plan and dive with blends up to 40%
Good to know: SSI renewed the Enriched Air Nitrox programme this week. The course has been updated and improved. Something many people do not realise: SSI study materials remain accessible for life in your MySSI account and programme updates are delivered automatically. Buy it once, stay up to date forever.
Who should consider nitrox?
Honestly, any diver, including those who typically do just one dive a day. The benefits increase when you want to do multiple dives in a day, such as on a liveaboard or an intensive dive week. Nitrox is one of the most practical specialties you can do. Not only do you gain more insight into the science behind diving, you also create the conditions to dive more safely.
We offer the SSI Enriched Air Nitrox specialty as a standalone course and in combination with guided dives, the AOWD course or other specialties. Get in touch to discuss the options.
