What was found
PRIOR TO PUSHBACK, WITH ALL DOORS CLOSED EXCEPT CREW ENTRANCE DOOR, RECEIVED AN ECAM ALERT FOR MAIN DECK CARGO SMOKE DETECTED MID & EXPERIENCED SMOKE IN COCKPIT FROM GASPERS. SMOKE ON SET RAPID & HIGHLY CONCENTRATED. SMOKE CLEARLY VISIBLE IN COCKPIT, APU BLEED AIR SELECTED OFF. FLIGHT CREW & LOAD CREW EXITED ACFT. APU HAD BEEN RUNNING FOR FIVE TO TEN MINS PRIOR TO SMOKE EVENT. AMM 21-51-00-03, OIL WETTING FOUND IN APU, APU WAS APROVED FOR R & R IAW W/C 4910000-00-00. OPS & LEAK CHKD GOOD. PERFORMED PACK BURN OUT, CHANGED COALESCER SOCKS IAW AMM 21-51-16-03-0. RAN BOTH ENGINES AGAIN AND RAN APU BLEED AIR FOR EXTENDED PERIOD OF TIME, NO SMOKE OR ODOR NOTED. ACFT OK FOR SERVICE.