As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SMKE - AFTER APU START AND PACKS ON, AN ACRID SMELL AND FA REPORTED SMOKE FILLED THE CABIN. TURNED OFF THE APU AND THE SMOKE/FUMES STOPPED. INSPECTED THE APU INTAKE AND RAN APU WITH SNIFFER TOOL AND FOUND NO CONTAMINATION OR SMELL. NO TROUBLE FOUND. REPLACED RECIRC FILTERS. FOLLOW-UP INSPECTION OF APU WAS NTF AND PRODUCED NO ODORS.