As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
STRONG ACRID ODOR STARTED JUST BEFORE DESCENT. COMPLIED WITH NO GO ODI PREVENTION PROGRAM. FOUND THE RT RECIRCULATION FILTER VERY DIRTY. R & R THE FILTER IAW AMM 21-25. R & R THE RT RECIRCULATION FAN IAW AMM 21-25. RAN APU, BOTH ENGINES, PACK AND CABIN EQUIPMENT, NO ABNORMAILITY NOTED.