The American Veterinary Medical Association (AVMA) Guidelines for the Euthanasia of Animals: 2013 Edition includes new recommendations concerning use of CO2 exposure as a method of euthanasia for laboratory rodents. These guidelines indicate that a gradual fill method must be used, with the recommended fill rate (displacement) between 10% and 30% of the chamber volume per minute. CO2 gas distribution systems should be equipped with an appropriate pressure-reducing regulator and flow meter combination (or equivalent) to permit precise regulation of gas flow to the chamber.
DLAM is in the process of equipping all of their CO2 euthanasia stations with the required pressure-reducing regulator and flow meter combinations. In addition the ARC is requiring that all labs with CO2 set-ups equip these stations with the required pressure-reducing regulator and flow meter combination. This requirement will be reviewed during semiannual inspections by the ARC and OARO inspection teams. When submitting an ARC protocol, if CO2 is indicated as a method for euthanasia of rodents, the Euthanasia Medications section must be updated to include the following in the Dose field for CO2: “animals euthanized by slow (20-30% per minute) displacement of chamber air with compressed CO2.”
(NOTE: the ARC recommends 20-30%, as a 20% fill rate is believed to be optimal)
If your CO2 tank is currently not equipped with a flow meter, flow meters may be purchased from commercial vendors [e.g., Patterson Scientific, WT Farley]. Note that the part(s) required will depend on your specific CO2 setup.
Please review the ARC Policy on Rodent CO2 Euthanasia available at http://ora.research.ucla.edu/OARO/Pages/ARC-policies/euthanasia-rodent.aspx and contact oaro@research.ucla.edu if you have any questions.