At what partial pressure of oxygen (PPO2) does oxygen toxicity become a concern?

Oxygen toxicity becomes a concern primarily when the partial pressure of oxygen (PPO2) exceeds 1.4 ATA (atmospheres absolute). At this level, the risk of adverse effects such as convulsions, lung damage, and other physiological problems increases significantly. This threshold is critical for divers using enriched air nitrox mixes, as exceeding this PPO2 during dives can lead to potentially dangerous situations.

In diving practices, it’s essential to maintain PPO2 levels within safe limits to mitigate the risks associated with prolonged exposure to elevated oxygen levels. While lower levels of PPO2, such as 1.0 ATA, are considered safe for most activities without immediate risk, as you approach and exceed 1.4 ATA, the likelihood of experiences such as central nervous system toxicity escalates.

Furthermore, while options implying higher ATA values (like 1.6 ATA) may also pose risks, the first significant threshold where oxygen toxicity becomes a prominent concern is established at 1.4 ATA, making this the critical value for divers to heed when planning their dives. This understanding is core to safe diving practices and managing dive profiles effectively with nitrox.