Rodent Euthanasia using Carbon Dioxide


Euthanasia is the act of humanely killing animals by methods that induce rapid unconsciousness and death without pain or distress. Carbon dioxide (CO2) is a commonly used method for rodent euthanasia. It is rapid, readily available, nonflammable and nonexplosive, minimally hazardous to personnel, and free from toxic tissue residues. There is ongoing controversy about the aversive nature of CO2, and this is an active area of research. This policy is intended to provide the current recommendations for the humane performance of euthanasia of rodents using CO2.



Guide for the Care and Use of Laboratory Animals, 8th edition, page 124


Rodents must be euthanized by trained personnel using appropriate technique, equipment, and agents. In particular:

  • The euthanasia chamber must allow ready visibility of animals. The chamber must not be overcrowded; all animals in the chamber must be able to make normal postural adjustments
  • Compressed gas in cylinders is the only permitted source of CO2.
  • Chambers must not be pre-filled with CO2 -- this method is unacceptable
  • The chamber should be gradually filled with CO2 at a rate of 10-20% volume per minute until animals lose consciousness, at which point the flow rate can be increased. For instance, a chamber with a volume of 10 liters would require a flow rate of 1-2 liters/minute
  • After respiratory arrest, a secondary method of euthanasia (e.g., thoracotomy, exsanguination, cervical dislocation) is required
Policy Adoption Date: 04/09/2013

Reference minutes: 04/09/2013