Scuba Diving International (SDI) Computer Nitrox Practice Exam

What is the most important measure to help avoid oxygen toxicity when diving Nitrox?

1. Never exceed a PO2 of 2.0

2. Limit dive times to under 30 minutes

3. Use a diving computer

4. Maintain a specific ascent rate

The correct answer is: Never exceed a PO2 of 2.0

Maintaining a partial pressure of oxygen (PO2) of no more than 1.4 to 1.6 ATA during recreational diving is critical in avoiding oxygen toxicity. When diving with Nitrox, which is a mixture of oxygen and nitrogen, it is essential to monitor the PO2 levels to ensure they remain within safe limits. Exceeding a PO2 of 2.0 ATA can significantly increase the risk of central nervous system toxicity, which can lead to serious complications such as seizures while underwater. Diving computers assist in monitoring various factors, including depth and time, but they do not specifically limit or guarantee safe partial pressures of oxygen. While limiting dive times and maintaining a specific ascent rate are important safety practices, they do not directly address the risk of oxygen toxicity as effectively as managing the PO2 levels does. Therefore, understanding and adhering to the appropriate PO2 limits is the most crucial factor in preventing oxygen toxicity during Nitrox diving.