PpO₂ — Partial Pressure of Oxygen

PpO₂ is the actual pressure of oxygen within your breathing gas mix. This value changes as you descend because water pressure increases with depth. Most recreational divers aim for a PpO₂ between 0.21 and 1.4 bar. If you breathe air at 30 m, your PpO₂ is 0.84 bar. High levels cause central nervous system toxicity. This often leads to seizures while you are underwater. I saw a diver in Koh Tao lose control because his nitrox mix had a PpO₂ of 1.6 bar at depth. Always check your computer settings before every descent. Use a dive computer to track your oxygen levels in real time. Never exceed 1.4 bar during active diving stages.