The Animal Welfare Committee recommended that CO₂ be phased out as a method of stunning pigs before slaughter within a period of five years. The independent advisory body, which advises Defra and the devolved administrations, published a report on the "impacts on pig welfare of stunning with high-concentration CO₂ gas and potential alternative stunning methods." The report states that exposing conscious pigs to high concentrations of CO₂ is associated with three main welfare concerns: pain, respiratory distress, and fear. The document analyzes the feasibility of other stunning methods, including exposure to a mixture of inert gases, such as argon or nitrogen. It notes that there are "technical challenges" in using inert gases in current CO₂ systems or modified systems. However, it states that immersion in argon "causes minimal immediate visible reaction, since these gases cannot be directly detected by the pig." "However, the induction of unconsciousness remains gradual, and it ...