A method of euthanizing air-breathing animals by replacing part of their air supply with the exhaust emissions of an internal combustion engine. The engine is mounted on a barrow that can be wheeled to the burrows of rabbits, gophers and the like. The engine runs initially on a lean fuel/air mix and later on extra fuel that raises the oxides of carbon content to 6%. The inclusion of fogging oil makes the emissions visible so that the operator is able to avoid breathing them. The emissions can be directed into chambers for euthanizing collected animals such as hens and scaled up in order to treat large volume areas such as grain silos in order to kill silo vermin.
