A B737-700 PLT RPTS THAT THE FLIGHT CREW THAT FLEW THE ACFT AFTER HE DID RPTED THE CREW OXYGEN VALVE MAY HAVE BEEN CLOSED.

Narrative

CREW THAT FLEW THE ACFT AFTER WE DID RPTED THE CREW O2 VALVE MAY HAVE BEEN CLOSED. CREW OXYGEN VALVE MAY HAVE BEEN CLOSED.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THEIR CARRIER HAS SOME NEXT GEN ACFT THAT USE STEEL OXYGEN BOTTLES; NOT JUST COMPOSITE TYPE. BUT; THE COMPOSITE BOTTLES SEEM TO BE THE FOCUS OF CONCERN DUE TO THE TEST PROC FOR THE 'PRESS TO TEST' OXYGEN MASK SUPPLY MAY NOT BE ADEQUATE ENOUGH FOR THE FLIGHT CREW TO IDENTIFY AN ACTUAL LOW FLOW IN THE SUPPLY LINE FROM A VALVE HANDLE NOT FULLY OPENED. OTHER CARRIERS; INCLUDING HIS; HAVE IMPLEMENTED A MINIMUM 5-SECOND 'PRESS TO TEST' PROC IN THEIR FLT OPS MANUAL. BUT; AFTER HIS MOST RECENT FLT; WHEN THE OUTBOUND CREW FLEW THE SAME ACFT HE CAME IN ON AND RPTED THE OXYGEN FLOW PROBLEM; THERE IS A FEELING THE 5-SECOND FLOW TEST MAY NEED TO BE REVISITED. RPTR ALSO STATED THEIR B737-700'S DO NOT HAVE A CREW OXYGEN SHUT-OFF VALVE IN THE COCKPIT; ONLY IN THE LOWER E/E COMPARTMENT AT THE BOTTLE ITSELF. HE DOES NOT KNOW IF THEIR CREW OXYGEN BOTTLES ARE REMOVED FOR SERVICING OR RE-SUPPLIED FROM AN EXTERNAL SERVICE PANEL ON THE ACFT.