Sample comparison between the observed CO and ¹³CO line ratios and the predictions from the RADEX model. The lines represent the observed line ratios ± the uncertainties in their determination. The comparisons are shown at the kinetic temperature at which the minimum value of ﹩{\chi }_{\mathrm{total},\min }^{2}﹩ is located. In the middle and lower panels, we show cases in which the 3σ upper limit of the ¹³CO ﹩J=1\to 0{/}^{12}\mathrm{CO}﹩ ﹩J=1\to 0﹩ and/or the ¹²CO ﹩J=7\to 6/J=3\to 2﹩ ratios are used to discard solutions.