Lethal effects of carbon dioxide on the roof rats

Abstract

Carbon dioxide (CO₂) was introduced into polyethylene chamber with the caged roof rats, Rattu rattus, inside a laboratory to examine its efficacy against them. When the gas was introduced at 50 liters/min. for 90 minutes into a 9.2 m³ volume at 20℃, all four rats caged on the floor level died within 25 minutes after gas release. However, all rats in the middle part (90 cm height) and upper part (180 cm) could survive for 80 minutes. In this case, the gas concentration rapidly reached 70% in 30 minutes. after gas release into the cage on the floor level. At that time, however, the gas concentrations in the middle and upper sites were 21% and 0.5%. After 90 minutes, an electric fan circulated the air, and the gas concentration became a uniform 47% throughout the chamber and paralyzed all rats. When the gas concentration was increased to 150 liters/min. all rats were knocked out within 130 minutes after gas circulation. The recommended CO₂ gas concentration for controlling rats is therefore 60% for 40 minutes.