As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT CREW REPORTED WHILE TAXING TO GATE AFTER LANDING IN SGF AND SWITCHING AIR CONDITIONING PACK TO THE APU THE CABIN FILLED WITH HAZE AND STENCH. MAINTENANCE DEPARTMENT PERSONNEL INSPECTED THE AIRCRAFT AND REMOVED AND REPLACED THE APU ASSY, IAW ALLEGIANT AIR TASK CARD R0594902. SYSTEM OPS CHECKS NORMAL AND THE AIRCRAFT WAS RETURNED TO SERVICE.