The compressed air at four atmospheres contains four times as many oxygen molecules as the same volume of air at surface pressure. This means that a given volume of high-pressure air can support breathing for longer than the same volume at the surface — a counterintuitive fact that is essential to understanding how Okene’s air supply lasted as long as it did.
The complicating factor is carbon dioxide. As a person breathes, they exhale carbon dioxide, which accumulates in a sealed space. At surface pressure, the accumulation of CO2 — rather than the depletion of oxygen — is typically what becomes the limiting factor for human survival in a sealed space. Eric Hexdall, a diving medicine clinical director at Duke University who commented on the Okene case, estimated that CO2 toxicity would become a concern after approximately 56 hours, with unconsciousness potentially following around 79 hours.
Okene was found after approximately 60 to 62 hours, which places him within what the diving medicine estimates suggest was a survivable but narrowing window. He had not lost consciousness. He was disoriented and physically depleted, but functional.
Whether the specific conditions of his air pocket — the pressure, the volume, the rate of CO2 buildup given the precise size of the space and the rate at which seawater may have continued to absorb some CO2 from the air — exactly match the general model is not something that can be confirmed from outside. The model explains how the survival was physically possible. It does not claim to have measured exactly what happened inside that four-foot space over sixty hours.