Just to add a bit of Danish levity:
I arrived in BLL one night and the loaders refused to work until I shut the APU down (I wanted to stay warm during a 20 minute turnaround).
"Why" said I?
"It makes too much noise and it says so in our rules"
So, I shut the APU down and switched on the Brake Fans (which made more noise than the APU).
That blew the whole union plan apart because there was nothing in their bits and pieces that mentioned Brake Fans and I pointed out that this was a matter of flight safety.
I think I won the moral high ground that night.
Very cunning: the conflict being that hot brakes are a safety hazard but so is APU noise. But the union boys and girls can't be expected to undertake work in an environment not fully conducive to safety (similar to a PIC always putting safety first) so the get out of jail free card (for them) was for you to run fans along with the APU (keeping your chestnuts warm while the brakes cooled - a form of heat exchange I suppose) and then everything is shut down to allow loading to begin. Makes for a long turn around, a delayed breakfast and knocks the schedule off track but everyone can claim the moral high ground. Perhaps not that cunning a plan once the loaders get the measure of it.