SPCA is concerned that the growing body of evidence indicates carbon dioxide (CO₂) is not a humane method of killing animals, despite its continued use in research, testing, and teaching. Currently, the use of CO₂ is recommended under strict parameters for concentration, flow rate, and the animal’s life stage. SPCA is concerned with the amount of time an animal experiences aversive states of welfare such as anxiety, air hunger, and pain before they become unconscious before death. Our organisation supports efforts to move away from the use of CO₂ as a killing method or to refine the use of CO₂ so that it is a less aversive experience for animals, such as mixing of other gases which would lead to unconsciousness sooner and with fewer side effects.

SPCA advocates for more funding and research into the refinement or phase-out of the use of carbon dioxide (CO₂) as a killing method.

Institutions that still use CO₂ to kill animals in research, testing, and teaching, should review current protocols to ensure they are consistently written and conducted in accordance with the 2020 American Veterinary Medical Association (AVMA) Guidelines for the Euthanasia of Animals. Institutions that use CO₂ to kill animals should ensure a secondary method of death is used to avoid the risk of an animal regaining consciousness.