What was found
STRONG ODOR AFTER ENG START FROM ROW 8 AFT. PERSISTED FOR 25 MIN ON GROUND IAW AMM 05-51-56-201. REMOVED AND REPLACED LT AND RT RECIRCULATION FAN FILTERS WRT 21-25-02-904-063-004. CARRIED OUT AMM 05-51-56-940-801-C1 UP TO DETAILED INSPECTION AND OPS CHECKED, ENGINE GROUND RUNS PERFORMED WITH PACKS BEING OPERATED ON ENGINE AND APU BLEED INDIVIDUALLY, NO SMELL EVIDENT THROUGH CABIN. INSPECTION CRITERIA MET AND SATISFACTORY FINDINGS. NO EVIDENCE OF EXTERNAL LEAKAGE DURING DETAILED VISUAL INSPECTIONS REF AMM 05-51-56-940-801-C1 UPTO STEP (K). DISPOSITION OF EVENTS FOLLOWED. FILTERS HAVE BEEN REPLACED. AIRCRAFT INSPECTIONS HAVE BEEN ACCOMPLISHED PER REQUIREMENTS OF AMM 05 -51-56.