Yes IR is different, also the NMR is. The CO2 has not rotational spectrum on microwave but HAS rotational spectrum on Raman. Other spectrum can also offer diferences (e.g. the electronic?).
Also measuring of dipolar momenta. The CO is a dipole.
Probably via measuring the diffusion of both. The viscosity is different. I did a similar experiment for detect different gases but experimental apparatus was rudimentarius and only gases with large difference in viscosity coefficients could be unambiguosuly detected.