What was found
CABIN FILLED WITH SMOKE WHILE BROADING PASSENGERS. APU CONFIRMED FAILURE. APU PNEUMATIC DUCT FROM APU FWD BULKHEAD TO STA 1743 NEEDS CLEANING DUE TO OIL INSIDE OF DUCT CAUSED BY APU MALFUNCTION. FOUND KEVLAR, MATERIAL (FOD) IN INLET OF OLD APU INLET SCREEN, NEED TO INVESTIGATE SOURCE, BEFORE INSTALLATION OF NEW APU. INSPECTED INLET DUCT, FOUND NO DETERIORATION. APU INLET DOOR APPEARS TO BE CHANGED IN RECENT HISTORY. SUSPECT LEFT OVER MATERIAL FROM OLD APU INLET DOOR. FIREWALL INSP COMPLETED, APU AIR INLET EXAMINED, FOUND GOOD. CABIN RECIRC FILTERS NEED TO BE RPL'D. RPL'D LEFT AND RIGHT RECIRCULATING FILTERS.