Nitrox Blends Compared: EAN32 vs EAN36 vs EAN40

Why blend choice matters

All nitrox blends do the same thing: lower the partial pressure of nitrogen at depth so your tissues on-gas slower, extending no-decompression limits compared to air. The trade-off is that they raise the partial pressure of oxygen, which caps the maximum operating depth at 1.4 ata (working) or 1.6 ata (deco/rest). Choosing the right blend is a depth/time optimisation, not a universal upgrade — diving EAN40 to 35 m exceeds 1.4 ata ppO₂ and risks oxygen toxicity. Use the mod-calculator to compute MOD and EAD for each blend, and the dive-planner to compare runtime and NDL on your specific profile.

EAN32 — Sweet spot for 18-30 m diving

EAN32 has a MOD of 33 m at 1.4 ata and an EAD on a 25 m dive of about 21 m on air tables. It's the most widely taught entry-level nitrox blend (PADI/SSI/SDI Enriched Air) and the de-facto holiday blend in tropical waters. On a 25 m × 40 min dive, NDL on EAN32 is roughly 28 minutes vs 17 minutes on air. Best for: liveaboards with 18-30 m reefs, training-dive sites at 20-25 m, anyone wanting NDL margin without sacrificing depth flexibility. Drawback: above 33 m it's off-limits at 1.4 ata. CNS load is low — 1.0 %/hour at 33 m — so back-to-back EAN32 dives carry no oxygen-tox issue for typical rec depths.

EAN36 — Repetitive 18-25 m dives

EAN36 caps at 28 m MOD (1.4 ata) and gives a clear NDL advantage on dives that hover around 20-25 m. EAD on a 22 m dive is about 15 m on air — that's a significant offset to tissue loading. On a 22 m × 50 min dive, NDL on EAN36 is around 50 minutes vs ~37 on EAN32 and ~22 on air. Best for: shallow wreck dives, training students at fixed 18-22 m platforms, photographers staying long at shallow reefs, dive masters running 3-4 dives a day. Drawback: 28 m MOD is restrictive on Indo-Pacific reef walls and most Mediterranean walls. CNS clock starts being relevant on multi-dive days — track total exposure with the dive-planner.

EAN40 — Maximum NDL extension, advanced cert

EAN40 caps at 25 m MOD (1.4 ata) and 30 m at 1.6 ata for deco. NDL on a 20 m × 60 min dive is essentially unlimited on EAN40 (well over 60 minutes); on air it's ~30. The trade-off: most agencies require an Advanced Nitrox or equivalent course to dive blends above EAN40 because the narrower MOD window and higher CNS load demand stricter gas-switch and ppO₂ discipline. Best for: shallow technical work (deco gas at 6-9 m has a different role — see bottom-vs-deco-gas), wreck penetration at 15-22 m, dive professionals doing repetitive 18-25 m work. Drawback: hard MOD at 25 m means a single uncontrolled descent past it is a real ppO₂ hazard.

How to pick your blend

Define the planned maximum depth before the blend, not the other way around. For a 30 m wall, EAN32 is the deepest blend that keeps you under 1.4 ata. For repetitive 22-25 m reef dives, EAN36 doubles your NDL. For shallow training at 18 m, EAN40 turns the dive into a near-unlimited time exposure. Cost rises with O₂ percentage — partial-pressure blending uses more oxygen — so check pricing locally. Compute MOD, EAD and predicted NDL for your exact profile in the mod-calculator and dive-planner before committing. Never assume yesterday's blend is right for today's site.