Effect of the CMB on the ﹩{L}_{\mathrm{FIR}}\mbox{--}{L}_{\mathrm{CO}}^{{\prime} }﹩ relation at z = 3 for a range of kinetic temperatures with ﹩{\bar{n}}_{{{\rm{H}}}_{2}}=1\times {10}^{2}﹩ cm⁻² (left), ﹩{\bar{n}}_{{{\rm{H}}}_{2}}=1\times {10}^{3}﹩ cm⁻³ (right), and ﹩{\bar{n}}_{{{\rm{H}}}_{2}}=1\times {10}^{4}﹩ cm⁻³ (bottom) calculated using RADEX. Data are recalculated from Greve et al. (2014) to use L_FIR as defined in the rest of this paper over the range of 40–500 μm. We fit only the z < 1 galaxies with orthogonal distance regression (ODR), and find ﹩{\mathrm{log}}_{10}({L}_{\mathrm{FIR}})=(0.90\pm 0.06){\mathrm{log}}_{10}({L}_{\mathrm{CO}}^{{\prime} })+(2.8\pm 0.6)﹩ and is shown by the solid line. The 3σ uncertainty in the ODR fit is indicated by the gray-shaded area. The high-redshift galaxies all appear to lie consistently above the z = 0 relation, consistent with the predicted CMB effects.