Carbon dioxide (CO2) stunning is used to make an animal unconscious just before slaughter. ‘Stunning’ is probably the wrong word as animals are not responding to a shock, which is the case with mechanical or electrical stunning methods.
CO2 stunning, like all methods involved in humane slaughter, must meet the following criteria:
There have been welfare concerns about CO2 stunning because it irritates the respiratory tract. However, research has produced conflicting results with some showing pigs tolerate CO2 stunning and some showing they do not. A sample of test results show:
A variation on CO2 stunning is a controlled atmosphere chamber that contains a mixture of nitrogen, argon and CO2 gases but no oxygen. Controlled atmosphere stunning is used pre-slaughter in some poultry-processing plants and on some poultry farms for euthanasia. Hens are unconscious within 20 seconds of being in the chamber. Argon and nitrogen are important for painless gassing, as using CO2 only may cause distress to the hens.
For further information, see: Model Code of Practice for the Welfare of Animals: Livestock at Slaughtering Establishments
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