Scuba Diving International (SDI) Computer Nitrox Practice Exam

What is the preferred minimum surface interval for Nitrox diving?

1. 30 minutes

2. 60 minutes

3. 90 minutes

4. 120 minutes

The correct answer is: 120 minutes

The preferred minimum surface interval for Nitrox diving is commonly recommended to be at least 120 minutes. This extended surface interval allows divers to off-gas nitrogen effectively from their bodies before making subsequent dives. Nitrox mixtures, being richer in oxygen and lower in nitrogen than regular air, can influence the way nitrogen is absorbed and released during diving. The longer surface interval helps to minimize the risk of decompression sickness as it provides additional time for nitrogen to leave the body, especially after deeper or longer dives. While shorter intervals such as 30 or 60 minutes may sometimes be deemed acceptable for specific conditions or guidelines, 120 minutes is viewed as a safer standard that better supports divers' health and safety. In summary, adhering to a minimum surface interval of 120 minutes is particularly advised for Nitrox diving to ensure adequate nitrogen elimination and to promote a safer dive experience.