Oxygen is a drug, and like any drug it has a dose above which it causes harm. Understanding oxygen toxicity is central to why hyperbaric protocols look the way they do.
Two forms
CNS (central nervous system) toxicity is the acute concern: at high pressures, excess oxygen can, rarely, provoke a seizure. The seizure itself is self-limited and leaves no lasting damage, but it must be avoided. Pulmonary toxicity is the slower concern: prolonged high-oxygen exposure over many hours can irritate the lungs, relevant mainly to very intensive or repeated treatment.
How rare is it?
CNS oxygen toxicity seizures occur in roughly 1 in 10,000 treatments at standard clinical pressures — uncommon, and made rarer still by protocol design.
How protocols prevent it
Three levers keep oxygen toxicity rare: pressure is capped (most treatment is at 2.0–2.4 ATA, not higher); session length is limited; and longer or higher-pressure treatments include scheduled air breaks — short periods breathing ordinary air that reset the exposure. Patient screening for seizure risk factors adds another layer.
Educational content, not medical advice — see our medical disclaimer. Terms in dotted teal link to the glossary.