Controlled atmosphere stunning using inert gas or low CO2 concentrations provides better welfare outcomes at slaughter than conventional water bath electrical stunning.
The transition from water bath to controlled atmosphere killing represents a genuine welfare advance for poultry because it eliminates the pre-stun welfare costs of live shackling, inversion, and electrical stunning of conscious birds. The welfare case for CAS is strongest when inert gas or multi-phase CO2 systems are used rather than simply switching from water bath to single-phase high CO2 exposure, which causes aversive respiratory distress before unconsciousness. The capital cost of transitioning to CAS systems is significant but is increasingly justified by welfare, worker safety, and meat quality benefits that align commercial and welfare incentives.