...and is also explosively flammable. Remember that CFCs replaced early refrigerants which were flammable and/or toxic. This memorable incident may be attributed to using a flammable refrigerant:
https://en.wikipedia.org/wiki/Cocoanut_Grove_fire
Personally, I'm against an absolutist ban on CFCs, since it was mainly their mass release into the atmosphere that caused problems, and they had great advantages in closed-system uses. This may surprise a lot of HN readers, but I have the same belief about PCBs[1] and chrysotile (white asbestos)[2] --- "the dose makes the poison". Literally everything is harmful to something in some way, so the right thing to do is to manage use such that we can maximise the benefit:risk ratio, instead of the frenzied "ban everything" attitude that seems far too pervasive today.
[1] https://www.mcgill.ca/oss/article/controversial-science-envi...
Anyway, I still wonder why ammonia fell into disuse as a refrigerent.
One reason might be that we had to evacuate our office when our small refrigerator in the pentry popped and vented all ammonia. It took a while to get sorted, and it can't have been much in that small unit.