Policy Number: 2003-018-v
Policy Title: Euthanasia of Rodents Using Carbon Dioxide

Purpose: 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. This policy is intended to provide the current recommendations for the humane performance of euthanasia of rodents using CO2.

POLICY: 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
  • Either medical-grade or industrial-grade CO2 is acceptable for euthanasia (only medical-grade CO2 is permissible for anesthetizing animals)
  • Compressed gas in cylinders is the only permitted source of CO2
  • Chambers must not be prefilled with CO2 – this method is unacceptable
  • The chamber should be gradually filled with CO2 at a rate of 10-30% 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 1-3 liters/minute
  • CO2 flow should be maintained for at least 1 minute after respiratory arrest
  • Animals must be attended during the entire euthanasia process; for safety and humane reasons it is not acceptable to turn on the CO2 and leave the animals
  • Neonatal rodents (up to 10 days of age) are resistant to the effects of CO2, therefore alternative methods (such as decapitation) are recommended for these animals
  • After respiratory arrest, a secondary method of euthanasia (e.g., thoracotomy, exsanguination, cervical dislocation) is recommended


Author: R. Lane, J. Welter
ePublication Date: 01/23/2003
History: Amended 9/2011; 1/2014; 4/2014; Reviewed, no changes 9/2017