As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER APU START WHEN BLEED AIR WAS SELECTED ON, WHITE SMOKE NOTICED COMING FROM GASPERS IN FLIGHT COMPARTMENT.REF MCN 62172-01 ISSUE 2 PARA 2A-B 1A REPLACED APU STARTER SHAFT SEAL REF Q400 AMM TASK 24-33-01-000-801 AND 24-33-01-400-801. PERFORMED REMOVAL OF ODOR FROM AC DUCTS REF Q400 AMM TASK 21-00-00-160-801. LEAK CHECK GOOD AND NO ODOR NOTED. NOTE THAT THE APU STARTER SHAFT SEAL IS WHAT WAS REPLACED.