¹²CO (top), ¹³CO, and HCN (bottom) excitation ladders of Arp 299 A with the flux of each transition plotted as black asterisks with red error bars. In blue, green and yellow dotted lines we plot the PDR/PDR/mCDR (left), PDR/PDR/mPDR (center), and PDR/PDR/XDR (right) ISM phases with their filling factors. The composite model is plotted with a red solid line. The model H₂ density [log cm^-3], G/G₀ [log Habing flux] or F_X [log erg s^-1 cm^-2], and percentage mechanical heating (α) are shown in the legend along with the relative contribution of each phase in terms of emission and column density. For emission, we compared the integrated intensity of each ISM phase to the total modeled CO flux (the red line). For the column density we perform the same calculation except comparing the column density of each phase to the total combined model column density.