The extended non-LTE model for the CO₂ infrared bands in the Earth atmosphere includes a set of 328 vibrational states of seven CO₂ isotopes (Shved et al., 1998). To simplify solving the non-LTE problem of radiative transfer in the CO₂ bands, a procedure of reducing the amount of the vibrational states is formulated. A hierarchy of three models, which are simplier than the extended model but provide a reliable accuracy of estimating non-equilibrium populations, is proposed. In the direction of decreasing accuracy, these simplified models include 206 and 117 states of seven CO₂ isotopes, and 60 states of five CO₂ isotopes, respectively. Even the simplest model allows evaluation the populations of the lower vibrational states with a reasonable precision. The errors in estimating the total non-LTE limb radiance for the 4.3 and 15 μm CO₂ bands with this model do not exceed the order of 10% and 1%, respectively. Use of the simplest model in evaluating the rate of net radiative heating in all the infrared CO₂ bands gives errors which do not exceed ∼ 0.01 K/day above about 80 km and increase down to the stratopause up to ∼ 0.04 K/day.