I hope hes not talking about the portable Ammonia fridges, that you vent by using some garden hose & venting the gas into a large bucket/drum of water...

Ammonia gas is a demon in a bottle. One wiff of it & you are choking to death.
Its also used in Drug labs & will get anybody some very intiminate attention by LEO.
One fridge would cover a city block with white unmistakable cloud.