Narrative:

I received a call from maintenance control regarding a crew oxygen mask discrepancy on a B757-200 aircraft. Upon arrival at aircraft [I] spoke to captain who advised that his oxygen mask would not test. After a brief time for troubleshooting; found captain's oxygen mask storage box to be suspect. After acquiring relative maintenance documents; I removed both aforementioned oxygen mask and storage box to obtain part numbers as to facilitate replacement serviceable parts/components. Upon parts arrival at gate; I verified part number on [the] serviceable tag and installed both components (I ordered an oxygen mask as a precaution). I then verified the operation of both box and mask; including a leak check at previously displaced fitting. All checked good per maintenance manual criteria. At this point I released the aircraft for service.during the input of pertinent data in my company's maintenance computer system; the oxygen mask that I had ordered and subsequently installed was flagged as being an incorrect part number for this aircraft. Mask part number removed from captains position was xxyy-107. Part number I installed was xxyy-107. However; in accordance with the company's illustrated parts manual (ipm); the part number should have been xxyy-108. As the aircraft had already departed; I was not in a position to remedy this. Contact was immediately made with maintenance control and engineering to advise them of this problem. The correct part number mask was installed in the captain's position at ZZZ a [day later].

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Original NASA ASRS Text

Title: A Lead Mechanic and Line Mechanic report installation of a Captain's oxygen (O2) mask that was not 'effective' for their B757-200 aircraft.

Narrative: I received a call from Maintenance Control regarding a crew oxygen mask discrepancy on a B757-200 aircraft. Upon arrival at aircraft [I] spoke to Captain who advised that his oxygen mask would not test. After a brief time for troubleshooting; found Captain's oxygen mask storage box to be suspect. After acquiring relative maintenance documents; I removed both aforementioned oxygen mask and storage box to obtain part numbers as to facilitate replacement serviceable parts/components. Upon parts arrival at gate; I verified part number on [the] serviceable tag and installed both components (I ordered an oxygen mask as a precaution). I then verified the operation of both box and mask; including a leak check at previously displaced fitting. All checked good per maintenance manual criteria. At this point I released the aircraft for service.During the input of pertinent data in my company's maintenance computer system; the oxygen mask that I had ordered and subsequently installed was flagged as being an incorrect part number for this aircraft. Mask part number removed from Captains position was XXYY-107. Part Number I installed was XXYY-107. However; in accordance with the company's Illustrated Parts Manual (IPM); the part number should have been XXYY-108. As the aircraft had already departed; I was not in a position to remedy this. Contact was immediately made with Maintenance Control and Engineering to advise them of this problem. The correct part number mask was installed in the Captain's position at ZZZ a [day later].

Data retrieved from NASA's ASRS site as of April 2012 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.