Physiology instrument

O₂ exposure — END, CNS% & OTU

Equivalent narcotic depth and oxygen toxicity load from the NOAA table and REPEX formula. A planning aid — always stay within your training.

About this tool

Two oxygen/narcosis tools — equivalent narcotic depth (END), and oxygen-exposure tracking (CNS% and OTU) for a dive or a day.

END: enter depth and mix to see how narcotic the dive feels vs air.
CNS/OTU: enter depth, time and mix to see ppO₂, CNS% and OTU against NOAA limits.
Add segments to build a running daily total.

Equivalent Narcotic Depth

How narcotic is this dive? END tells you the equivalent air depth for nitrogen narcosis.

Planned depth (m)Mix O₂ %

Treat O₂ as narcotic

END

24 m

✓ EAN32 at 30 m has an END of 24 m — equivalent narcosis to air at that depth.

O₂ narcosis: agencies disagree; PADI/SSI treat O₂ as non-narcotic. Toggle above reflects your training agency's assumption.

CNS% & OTU — oxygen exposure

Single-segment oxygen toxicity load. CNS limit from the NOAA table; OTU via the REPEX formula.

Depth (m)Mix O₂ %Time (min)

ppO₂

1.28

CNS%

16.2%

OTU

43.6

✓ CNS 16.2% — well within NOAA limits for this segment.

Planning aid only. Always dive within your training and current certification limits.

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