There is a law against using ammonia as a refrigerant in places where a leak could endanger people. It is a better refrigerant than the freon based.
But, our corrupt government has handed out “exceptions”. I know that the Dallas American Airlines Center ice system (for the ice hockey) runs on Ammonia.
and the place seats 10’s of thousands.
It is used a lot on corn by farmers.
Which is why in the pre-freon days, refrigerators and freezers were kept outside on the front porch, due to the ammonia gas that was used.
It is TO THIS DAY used in RV refrigerator cooling systems. They are listed as captive systems but they do smell REALLY BAD when they leak.