Farmed Pig CO2 Gas Stunning Welfare Concerns

Carbon dioxide gas stunning is used for the majority of pigs at slaughter in the UK and Europe. Scientific evidence shows it causes significant aversion and distress before unconsciousness.

Key Facts

Over 70% of UK pigs are stunned using high-concentration CO2 in gondola systems
CO2 causes a burning sensation in the airways and acute panic before loss of consciousness
Pigs show visible distress - vigorous struggling, squealing and hyperventilation in CO2 chambers
The period of aversion lasts approximately 15-30 seconds at high CO2 concentrations
Lower CO2 concentrations with nitrogen or argon cause less aversion but are not widely adopted
Controlled Atmosphere Stunning (CAS) with non-CO2 gases can achieve rapid, apparently aversive-free unconsciousness
Industry has been slow to transition from CO2 despite scientific evidence of its aversive nature

Welfare Considerations

CO2 stunning is the dominant killing method for pigs in the UK and most of Europe despite clear scientific evidence that it causes suffering. The aversion period - while pigs experience burning airways and panic before losing consciousness - represents a predictable welfare failure at an enormous scale: millions of pigs per year. The technology for less aversive alternatives exists. The barrier is primarily economic - CO2 systems are cheaper to install and operate than alternatives using argon or nitrogen. This is a case where the welfare cost is measurable, alternatives exist, and regulatory pressure is the primary lever for change.

What You Can Do

Support campaigns by Animal Aid, Humane Slaughter Association and Compassion in World Farming for CO2 stunning reform
Choose pork from producers that use non-CO2 alternatives where possible
Advocate for regulatory review of CO2 stunning standards in UK post-Brexit law
Reduce pork consumption as a direct response to slaughter welfare concerns
Support research into rapid-onset, low-aversion alternatives to CO2 stunning for pigs