Environmental Conditions in a Chamber with Dry Ice

Dry ice is used in research laboratories as a source of CO2 for euthanasia of rodents. The present study was performed to evaluate environmental conditions created in a standard (9-liter) bell jar. By using a portable gas analyzer and measuring at 7.5 cm above the platform, we evaluated the chamber filling rate at room temperature with a known quantity of dry ice, maintenance of 70% CO2, and concentration of CO2 maintained when the top of the chamber was removed and replaced. Ambient temperature in the chamber and temperature of the platform were also measured. Results indicated that 500 g dry ice was required to maintain the filling rate and CO2 concentration at levels recommended by the American Veterinary Medical Association Panel on Euthanasia; that after removal of an animal, the lid should be replaced for 1 min before placing another animal in the chamber; and that although ambient temperature in the chamber never fell below 178C during an 80-min period, the platform temperature decreased to 08C. If a chamber must be used as described above for more than 1 h, consideration should be given to alternating between two chambers and allowing a chamber to warm to room temperature before reuse.