I was reading an interesting thread on APC and the question and concerns of a “wet sock smell” came up.
To my understanding, it only happens when you run the packs from the bleed air (and just about every plane is designed that way). Some said it was mold in the filter and some said that it was a leaky APU so it’s actually a oil that into the bleed air system.
From what I’ve read, some people have gotten pretty sick or even lost medicals over it.
Either way, being that 319/320 and 145 are heavy offenders of this (again, from what I’ve read), I was hoping you guys could shed some light on this topic?