PADI Enriched Air Nitrox: More Bottom Time on Every Dive
Online May 11, 2026
Want more bottom time? PADI Enriched Air Nitrox! If you've been certified for a while and started paying attention to your dive computer, you've probably noticed how quickly the no-decompression clock ticks down on a second or third dive of the day. You surface with plenty of air in your tank but your bottom time is gone.
Enriched Air Nitrox is the most direct fix for that problem. It's the most popular PADI specialty certification in the world, and it takes about a day to complete.
Here's what it actually is and whether it's worth your time.
What enriched air nitrox is
Regular scuba tanks are filled with air — the same stuff you're breathing right now, which is roughly 21% oxygen and 78% nitrogen. Enriched air (also written as EANx, or just nitrox) is a gas blend with a higher percentage of oxygen and less nitrogen. The two most common mixes are 32% and 36% oxygen.
Less nitrogen in the mix means your body absorbs it more slowly during a dive. That translates directly into longer no-decompression limits at any given depth.
A simple example: on air, your no-decompression limit at 60 feet is around 55 minutes. On a 32% nitrox mix, that same depth gets you closer to 95 minutes before your computer wants you to surface. That's not a small difference.
The main reason people get nitrox certified
Bottom time. That's it for most divers.
If you've been on a liveaboard or a dive trip where you're doing three or four dives a day, you already know the frustration. By the third dive, your residual nitrogen from earlier dives cuts your allowable time significantly, even though your tank is full. Nitrox pushes those limits back.
On a week-long trip to a place like Bali or Little Cayman, the difference adds up. You get more time on the reef, more time watching the thing you came to see, and less time floating on the surface waiting for your surface interval to clear.
The secondary benefit people don't expect
A lot of divers report feeling less tired at the end of a nitrox dive day compared to the same day on air. The research on this is mixed, but the anecdotal evidence from divers who've made the switch is pretty consistent.
The likely explanation is that you're absorbing less nitrogen, which means your body is doing less work processing it out during off-gassing. Whether or not the science fully supports it, the fatigue difference is noticeable enough that most divers who get nitrox certified stick with it.
The tradeoff: depth limits
More oxygen in the mix sounds strictly better until you go deep enough that it isn't.
Oxygen becomes toxic to the central nervous system at high partial pressures. At depth, where ambient pressure increases, the effective oxygen dose from your tank goes up even though the percentage in the mix stays the same. On 32% nitrox, the maximum operating depth is 111 feet. On 36%, it's 95 feet.
For most recreational diving, this isn't a real constraint. The majority of dive sites worth visiting are well within those limits, and the increased bottom time you get at shallower depths is the whole point. But if you regularly dive deep wrecks or walls that drop past 100 feet, you'd be planning those dives on air anyway and switching to nitrox for the shallower dives in the same day.
Your dive computer needs to be set for the mix you're using before the dive. If your computer is set to air and you're breathing 32% nitrox, the no-decompression limits it shows you are conservative enough that you're not in danger — but you're also not getting the benefit you paid for. The course teaches you how to set up and verify your equipment correctly.
What the PADI Enriched Air Diver course covers
The course is primarily knowledge-based. You'll learn how nitrox affects your dive planning, how to calculate maximum operating depths for different mixes, how to analyze a tank to verify the actual oxygen content before a dive, and how to set up your computer correctly.
There's no special pool session required. The certification is completed without mandatory open water dives, though many shops include them. At Underwater Phantaseas, we can get you through the course in a single day.
Who it's right for
Anyone who dives more than a couple of times a year. The certification doesn't expire, and a nitrox fill typically costs the same as an air fill or just a few dollars more. Once you have the card, you have it.
It's especially useful if you're planning a trip. Getting certified before you go means you can use nitrox on every dive of the trip rather than doing the course on day one and missing out on the first day of diving.
It's also a natural complement to the Altitude Diver specialty if you're doing local Colorado dives regularly. Altitude already compresses your no-decompression limits. Nitrox gives some of that margin back.
The short version
Enriched air nitrox is one day, gives you more bottom time on every dive afterward, and is the most widely used specialty certification in recreational diving for a reason. If you're doing multiple dives per day or planning a trip, it pays for itself the first time you use it.
The PADI Enriched Air Diver course is available at our Lakewood shop. Call 303-988-6725 or enroll here and we'll get you set up.
Underwater Phantaseas is a PADI 5 Star IDC in Lakewood, CO. We've been training Denver divers since 1982.
