Hi there
Our experience, in the former national airline of Ireland,when we had 146s, was fumes in the cockpit and cabin, CCMs complaining of nausea, occasional vomiting and severe headaches of CCMs.Culprits included excess APU oil fiiling (easy to do in a 146) leading to fumes from spilt oil in the APU bay getting drawn into the airconditioning ducts and then into the cabin.Sometimes, the main engines were to blame.Deicing fluid entering the airducts also contributed....The trick of running the packs until they were hot, before flight, sometimes worked but sometimes it just made things worse.It was routine to board, start the APU, run the packs at full blast and open all the doors and sliding cockpit windows before the crews boarded, on a suspect aircraft...incidentally, the APUs were always oily.I've never seen a "dry" one.We also had to clean out all the big air ducts thoroughly during checks.
regards
TDD