[Amethyst_ice]

Some feeder breeders do use them lots yes.

In my case, with pet breeders, it is more because they may have larger numbers of rats so to reduce euthanasia costs with illness/ old age.

Labs use CO2 chambers and they are a humane method if correct. However, it is a lot of responsibility to put on yourself and bluntly speaking, if you only have one or two pets, not a cost effective method.