I agree 3rd Dick,
Once you start running the Fumes checklist, that is game over for that aircraft and crew in my company.
We have had a significant number of events in the past, leading to a change in the shutdown procedure for the APU/Batteries at last flight of the day, to try to avoid the “wet sock” smell on start up the next day.
Once “fumes” are reported or detected, MASKS ON, PUSH TO LEVEL, RUN Checklist, get on the ground in a timely manner, it may be the precursor to a greater emergency.