Narrative:

Climbing through FL230 first officer and I heard an unusual 'air leak' sound prompting us to investigate the integrity of crew oxygen supply system. Upon examination; we noted that the system pressure was decreasing approximately 80-100 psi per hour. We reset all O2 mask assemblies without apparent success. Pressure drop continued unabated; eventually decreasing from 1683 to 1496 psi. We were in contact with our company for the duration of this event and it was jointly decided to divert to [a suitable alternate] rather than attempt an oceanic crossing with a probable defective system.

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Original NASA ASRS Text

Title: A330 Captain reported diverting to an alternate after noticing the crew oxygen system had developed a leak.

Narrative: Climbing through FL230 First Officer and I heard an unusual 'air leak' sound prompting us to investigate the integrity of crew oxygen supply system. Upon examination; we noted that the system pressure was decreasing approximately 80-100 PSI per hour. We reset all O2 mask assemblies without apparent success. Pressure drop continued unabated; eventually decreasing from 1683 to 1496 PSI. We were in contact with our company for the duration of this event and it was jointly decided to divert to [a suitable alternate] rather than attempt an oceanic crossing with a probable defective system.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.