The standard in modern poultry processing plants is to render birds insensible—that is, unconscious and incapable of feeling pain—prior to slaughter. The process is known as “stunning.” ... The gas mixture deprives birds of oxygen, causing them to lose consciousness.

Does stunning kill chickens?

Electrical stunning works in two ways, affecting the brain and the heart. A high current (mAmps) and low frequently (Hz) will stop the heart and disrupt the brain, inducing unconsciousness. This combination will kill the chicken even before their throat is cut.

What gas is used to kill chickens?

In phase one, birds are exposed to carbon dioxide up to a concentration of 40% for a period long enough to render them unconscious. They then continue into the second phase, whereby the concentration of CO2 exceeds 40% and the birds are killed.