  Infra-red maps and profiles with high spatial resolution were obtained for
two single crystal diamonds with pronounced CO2 IR absorption peaks. Detailed
examination allows unambiguous assignment of the spectral features to solid
CO2-I phase. It is shown that the distribution of IR band positions,
intensities and widths in the sample follows regular patterns and is not
chaotic as was suggested in previous works where spectra of a few individual
spots were analysed. Consequently, pressure effects alone fail to explain all
observed features and shifts of the CO2 bands. Experimental data can be
explained by presence of impurities (such as water, N2, etc.) in the trapped
CO2. This implies that spectroscopic barometry of CO2 microinclusions in
diamond may be subject to poorly controlled bias. However, barometry is still
possible if Davydov splitting of the CO2-I {\nu}2 band is unequivocally
observed, as this indicates high purity of the CO2 ice.
