How to Plan a Nitrox Dive
A 5-step recreational workflow — pick the blend, know your gas, stay inside NDL
1. Pick your blend (EAN32 vs EAN36)
Recreational nitrox lives between EAN32 and EAN36, and depth is what picks the blend. At 1.4 ata, EAN32 has a MOD of 33 m and EAN36 a MOD of 28 m — so EAN36 is for shallow reefs and wrecks (18-28 m), EAN32 is the all-rounder up to 33 m, and air or EAN28 are better choices below 33 m. The MOD calculator also gives EAD, which is what your air-table or computer effectively sees for nitrogen loading. Example: EAN32 at 24 m has an EAD of about 19 m — that is why nitrox stretches your bottom time. Always verify the analyzed FO₂ on the cylinder before the dive; never trust the label.
→ Pick your blend (EAN32 vs EAN36)2. Establish your personal SAC
Your Surface Air Consumption is the foundation of every gas-planning number that follows. Without a real SAC, Rock Bottom is a guess. Typical recreational SAC ranges from 12 L/min (calm, experienced, neutral) to 20 L/min (cold water, current, fresh from the course) — but the only number that matters is yours. Use the SAC calculator after a dive with cylinder size, start/end pressure, average depth, and elapsed time, and log it across at least 8-10 dives in varied conditions to build a representative average. Example: a 24 m, 45 min dive consuming 130 bar from a 12 L cylinder gives a SAC of about 14.4 L/min. Keep separate baselines for warm and cold-water trips.
→ Establish your personal SAC3. Check your NDL on nitrox
The reason recreational divers blend nitrox is to extend the No-Decompression Limit at the same depth — less nitrogen in the mix means less nitrogen loaded into your tissues. Using the Gradient Factors tool with Bühlmann ZH-L16C (Baker 1998), a moderately conservative 40/85 setting at 24 m gives roughly 40 min NDL on air versus about 70 min on EAN32. Staying within NDL keeps the dive a no-stop ascent with only a discretionary safety stop — no mandatory deco obligation. Plan your run-time so that turn-around and ascent finish well before NDL, and pad with a 3 min stop at 5 m. Tighten GF to 30/80 if you are cold, tired, or post-flight.
→ Check your NDL on nitrox4. Calculate Rock Bottom reserve
Rock Bottom is the minimum pressure that must remain in your cylinder to bring two divers safely to the surface from depth after a worst-case event — out-of-gas buddy, elevated breathing, slow ascent, and a safety stop. Use a 1.5x stress multiplier on calm shore dives and 2x on boat dives in current or low visibility. Example: at 24 m with a 12 L cylinder, SAC 14 L/min, and a 2x multiplier, Rock Bottom lands around 60-70 bar — so you turn the dive at 100-110 bar, not at 50 bar. If Rock Bottom exceeds your planned turn pressure, switch to a 15 L cylinder or pick a shallower site. Recalculate whenever depth, team, cylinder, or SAC changes.
→ Calculate Rock Bottom reserve5. Plan the second dive of the day
Nitrox does not erase residual nitrogen — it just slows down the loading. On a boat trip or liveaboard, the second and third dives of the day still carry tissue nitrogen from the first, and the Successive Dives tool tracks it across the surface interval using Bühlmann ZH-L16C compartments. Example: an EAN32 dive to 24 m for 50 min followed by a 1 h 30 min surface interval gives a second-dive NDL at 18 m of roughly 50 min on EAN32 — well below the single-dive limit. Plan the deepest dive first, taper depth across the day, keep surface intervals at least 1 h, and skip the third dive if NDLs collapse or fatigue sets in. Avoid flying for 18 h after the last dive (24 h after multi-day repetitive).
→ Plan the second dive of the day