Gas stunning (controlled atmosphere killing) is increasingly used in poultry processing as an alternative to electrical water bath stunning, with distinct welfare implications.
Gas stunning welfare depends critically on the gas mixture and concentration used. High CO2 systems cause a period of breathlessness and distress before insensibility. Low-oxygen inert gas systems (helium, argon, nitrogen) avoid this aversive phase but are more expensive. The elimination of live conscious shackling is a significant welfare benefit of whole-house CAS systems over conventional water bath stunning regardless of gas mixture.