Has anyone ever ...

Yes I have had one. It was plant where they put some ammonia to force rodents out in case they are got in with load.
My first though was it was my reefer system leak.

 

Had drivers trained by DuPont to use a sample pump and Dragger tube with a reagent to sample the atmosphere inside a trailer. if the tube turned purple from the reagent, they had to don Self Contained Breathing Apparatus and plug and dike to go in and seal the leaking drum.

Ammonia is the easiest chemical to detect by smell; you can smell a fart's worth in a whirlwind...that's one of the reasons they still use it