What is the maximum partial pressure of oxygen (PO2) you should not exceed to avoid CNS oxygen toxicity?

To avoid central nervous system (CNS) oxygen toxicity, the maximum partial pressure of oxygen (PO2) that divers should not exceed is 1.4 ata/bar. This limit is grounded in research and studies conducted on the physiological effects of increased oxygen levels, particularly during deep scuba diving.

At a partial pressure of oxygen greater than 1.4 ata/bar, there is an increased risk of developing CNS oxygen toxicity, which can manifest in symptoms such as visual disturbances, muscular twitching, and seizures. This risk arises because higher pressures of oxygen can lead to the production of reactive oxygen species, which can cause damage to neural tissues and ultimately result in toxic effects.

Understanding this threshold is crucial for dive planning and safety, as it helps divers manage their exposure to oxygen, particularly when using mixed gases in deeper dives or rebreathers. Staying within this limit allows divers to take advantage of the benefits of oxygen while minimizing the associated risks.

When considering other values, 1.0 ata/bar is far too low for recreational or technical diving purposes, as it would not provide sufficient oxygen for normal breathing at depths requiring a higher PO2. The values of 1.2 ata/bar and 1.6 ata/bar are also above the