What was found
ACRID SMELL AFTER TAKEOFF AND INCREASINGLY WORSE THROUGHOUT THE FLIGHT. SMELL INCREASED FROM SMELL ON GROUND. ACCOMPLISHED TSM 21-00-00-801-810 TO CHECK FOR OIL IN THE APU BLEED AIR SYSTEM, BOTH EXTERNALLY AND INTERNALLY. ALL DUCTING REINSTALLED AND BAY SECURED PER 49-11-11-400-001. NO EVIDENCE OF OIL OR GREASE FOUND. REMOVED AND REPLACED BOTH L/R OZONE FILTERS PER CARD S2C21301. LEAK CHECK GOOD. REMOVED AND REPLACED RECIRCULATION FILTERS PER CARD S2B21301. RECIRCULATION FILTERS (P/N QA06423-01), OZONE FILTER (P/N 20499001), (S/N 0539), TT: 10081, TC: 4633, TSR: 998.