■Diving time management for a single dive per day

If you take more than 24 hours of surface interval from the last dive and perform the second dive, you do not have to worry about the oxygen accumulation in the previous dive.

Depending on the oxygen ratio of Nitrox used, the safe time for oxygen poisoning is different.

The time that is safe against oxygen poisoning is called the oxygen exposure limit, which can be calculated using the oxygen ratio exposure table.

Oxygen ratio exposure table

For example, when dive to 20 m depth using EAN32, the oxygen ratio of EAN32 is 0.32, so using the calculation formula for the oxygen partial pressure,
Oxygen partial pressure = 0.32 (20/10＋1) = 0.96.
In the leftmost column of the table, look for the closest number above 0.96.
1.20 is the closest number.
The oxygen exposure limit is 210 minutes shown in the right column.

Also, when dive to 25 m depth using EAN36, the oxygen ratio of EAN32 is 0.36, so using the calculation formula for the oxygen partial pressure,
Oxygen partial pressure = 0.36（25÷10＋1）＝1.26.　
In the leftmost column of the table, look for the closest number above 1.26.
1.30 is the closest number.
The oxygen exposure limit is 180 minutes shown in the right column.