A300
Maintenance Airframe; Maintenance Powerplant
Maintenance Technician 27
Workload; Communication Breakdown
Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
Human Factors; Procedure
Oxygen masks were pulled for installation on aircraft for completion of an Engineering Order (E.O.) by another member of the maintenance team. These sat on a bench until the second to the last day of the maintenance check. Due to the maintenance deferrals scheduled to be worked during the check; I had to complete much of the inspection and maintenance while my partner troubleshot the deferrals in-order to keep to schedule. (The last day we reserve for paperwork; parts ordering and taking inventory; except if it is needed to perform work on the plane.) This caused me to develop stress due to the additional workload put upon myself and also due to fatigue from having trouble sleeping.This situation caused me to trust my fellow teammate's selection of oxygen masks on the bench without verifying the Part Number (PN). Later; I discovered that the reason the wrong masks had been pulled for installation is that the masks for the A300 were intermixed with those for B767.The discrepancy was caught when the parts tag was processed and the masks were replaced.  The masks for each aircraft are being kept separately from each other and each member of the team is now responsible for pulling his own parts.
During a Maintenance Check on an A300 aircraft; the incorrect part number O2 masks were installed in the Cockpit. This occurred because O2 masks from a B767 were at the same location and the part numbers were not verified as to which masks were correct for this aircraft.