PADI Divemaster Certification Practice Exam

To avoid CNS oxygen toxicity, what is the recommended maximum partial pressure of oxygen?

1. 1.0 ata/bar

2. 1.2 ata/bar

3. 1.4 ata/bar

4. 1.6 ata/bar

The correct answer is: 1.4 ata/bar

The recommended maximum partial pressure of oxygen to avoid central nervous system (CNS) oxygen toxicity is 1.4 ata/bar. This level is based on extensive research and practical experience in diving, as well as guidelines provided by organizations such as PADI and NOAA. When divers breathe oxygen at elevated pressures (as encountered in technical diving or certain types of mixed gas diving), there is a risk of CNS toxicity, which can lead to symptoms such as visual disturbances, seizures, and loss of consciousness. The threshold of 1.4 ata/bar is considered a safe upper limit for breathing oxygen under pressure, allowing for safe diving practices while minimizing the risk of adverse neurological effects. Diving at partial pressures higher than 1.4 ata/bar significantly increases the risk of CNS toxicity, especially if exposure is prolonged. Therefore, operational protocols typically enforce this threshold to ensure diver safety during dives that involve enriched oxygen mixtures. Understanding the physiological effects of oxygen under pressure is crucial for divers to effectively manage their safety and optimize their diving practices.