Tools
Gas Specs
Analyse any nitrox or trimix mix at any depth: PPO₂, equivalent air depth (EAD), equivalent narcotic depth (END), gas density, and maximum operating depth (MOD).
Last updated 3 czerwca 2026
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What it is
Gas Specs takes a breathing mix and a depth, then tells you everything that matters about how that gas behaves there. Where Best Mix designs a blend for you, Gas Specs analyses one you already have. Set the oxygen and (for trimix) helium fractions, set the depth, and read the numbers.
The in-app title is “Gas Specs” (the same name appears on the home card and in the header). Internally the tool is the gas analyzer at the plan/ead-ppo2 route, so older references to “EAD/PPO₂” or “Gas Analyzer” point at this same screen.
How to use it
Set the oxygen
Add helium if it's trimix
Set the depth
Read the stats panel
Every input card has both a slider and a tap-to-type number field with plus and minus steppers, so you can drag for a quick estimate or type an exact figure. O₂ runs 5 to 100%, He 0 to 100%, and depth 1 to 300 m. The tool opens at air (21% O₂, 0% He) at 12 m.
Depth follows your unit setting, so the slider reads in metres or feet. PPO₂ is always reported in bar, never converted.
What each output means
Each value shows a short field label, with the descriptive phrase as a smaller subtitle beneath it.
| Output | Shown in app | Meaning |
|---|---|---|
| Oxygen partial pressure | PPO₂ (bar value) | Partial pressure of oxygen: PPO₂ = FO₂ × absolute pressure. The toxicity number. |
| Equivalent air depth (EAD) | EAD (subtitle “Equivalent air depth”) | The depth at which plain air gives the same nitrogen loading as your mix. Lets you reuse air-based no-deco thinking on nitrox. Helium is excluded. |
| Equivalent narcotic depth (END) | END (subtitle “Equivalent narcotic depth”) | The air-equivalent depth for narcosis. Tells you how clear-headed the mix keeps you at depth. |
| Maximum operating depth, working | Working MOD (subtitle “PPO₂ 1.4”) | Deepest depth at a 1.4 bar working limit, for active swimming. |
| Maximum operating depth, deco | Deco MOD (subtitle “PPO₂ 1.6”) | Deepest depth at a 1.6 bar limit, for resting and deco stops only. |
| Gas density | Gas Density (g/L value) | Real density of the mix at depth. Dense gas is hard to breathe and traps CO₂. |
| Equivalent air density depth (EADD) | EADD (subtitle “Density Equivalent”) | The depth at which air has the same density as your mix, a quick read on breathing effort. |
| Minimum breathable depth | Min Depth (subtitle “Hypoxic”) | For hypoxic mixes only: the shallowest depth where PPO₂ reaches the 0.16 bar floor and the gas is safe to breathe. |
The panel shows both MODs at once: a Working MOD at PPO₂ 1.4 and a Deco MOD at PPO₂ 1.6, so you can see the active-swim limit and the deco-stop limit side by side without changing a setting.
Narcotic-gas assumptions
EAD and END both convert a partial pressure back into the depth on air that would produce it, using the absolute pressure for your water type:
- EAD uses the nitrogen fraction only. It finds the depth at which air’s nitrogen partial pressure matches your mix’s, then reports that depth. Helium is treated as non-narcotic and excluded, since EAD measures nitrogen loading (your decompression reference), not narcosis.
- END depends on whether you count oxygen as narcotic. This is the “O₂ is Narcotic” toggle in Dive Settings. With it off, only nitrogen narcoses, so END equals EAD. With it on, everything except helium narcoses (nitrogen plus oxygen), which raises your END at the same depth. Turning it on is the more conservative reading.
Gas density uses standard surface densities (O₂ 1.429, N₂ 1.251, He 0.1786 g/L) scaled by absolute pressure, and EADD compares that against air’s surface density.
Warnings
The stats carry status colours and the screen raises alerts for the dangerous cases:
- High PPO₂. Above the 1.4 bar active limit the tool flags the value as deco-only and warns to avoid it during active swimming. Above 1.6 bar it warns of seizure and blackout risk.
- Gas density. Above 5.2 g/L it cautions and suggests adding helium. Above 6.2 g/L it warns of CO₂ buildup and tells you to add helium or reduce depth. Both limits are user-adjustable defaults (5.2 and 6.2 g/L), set in the deco and gas defaults.
- Hypoxic mix. If PPO₂ falls below the 0.16 bar breathable floor the tool marks the mix hypoxic and shows the depth above which it’s unsafe to breathe.
The O₂ and He sliders cannot produce an impossible mix. Raising O₂ past 100 − He percent automatically lowers He (and raising He past 100 − O₂ percent lowers O₂), so the two fractions always sum to 100% or less.
Behaviour and limits
Gas Specs reflects only the numbers you type in. It assumes the mix is exactly what you entered, so analyse and label your real cylinder before diving.
Related
- Best Mix Calculator designs the mix that Gas Specs analyses.
- Deco Planner uses the same PPO₂ and MOD logic to schedule gas switches on a full dive.
Parts of this guide were drafted with AI assistance and may contain mistakes. It's educational, not a substitute for training. Always dive within your certification and verify with your instruments.