Oxygen time limit answers how long can I stay at this ppO₂? It returns the NOAA single-exposure time for one partial pressure of oxygen, the time at which the CNS clock reaches 100 %, and the time to the single-day OTU limit.

What you enter

• From: ppO₂, to type the partial pressure, or Mix and depth, to have the tool work it out.
• ppO₂ (bar): the partial pressure breathed.
• Oxygen (%) and Depth (m): shown instead with Mix and depth. The ppO₂ assumes salt water at sea level.

There is no time field: the time is the answer.

Reading the result

• Single-exposure limit (min): the main figure, the NOAA time allowed at this ppO₂ in one exposure. It reads No limit below 0.5 bar.
• 300 OTU in (min): how long until the pulmonary dose reaches the single-day limit, or Never below 0.5 bar.
• ppO₂ (bar): the partial pressure used.

This tool reports times, not a judgement, so its figures carry no rails or colours. The verdict restates the main figure, for example At 1.40 bar, one exposure reaches 100 % CNS after 150 minutes. Between the table’s rows the tool works the time out from the rows either side.

What shortens the limit

• Earlier exposure. The times are for one exposure from a clean start. Oxygen already breathed the same day, on this dive or an earlier one, leaves less. The planner accounts for it; this tool does not.
• ppO₂ above 1.6 bar. The NOAA table stops at 1.6 bar. Above it the tool holds the 1.6 bar figure of 45 minutes, which overstates the time allowed.
• Reaching the limit. 100 % CNS is the end of the tabulated allowance, not a target. The planner warns from 80 %.

Next

• CNS and OTU reads the exposure for a set time.
• Oxygen exposure covers the clocks on a whole plan.