Volume 20 provides critically evaluated data on free molecules, obtained from infrared spectroscopy and related experimental and theoretical investigations. It is divided into four subvolumes: diatomic molecules; linear triatomic molecules; nonlinear triatomic molecules; and polyatomic molecules. Subvolume B2 contains data for C02 (OCO) and has been spilt into two parts. This is the second part, and it deals with 13 isotopic varieties of C02.