A plot of the line ratios relative to the integrated intensity of the CO J = 6 − 5 as a function of mass-loss rates. In the lower panel: for ortho-H₂O 1_1,0 − 1_0,1 (squares), para-H₂O 1_1,1 − 0_0,0 (circles), NH₃ 1₀ − 0₀ (triangles) scaled up by a factor of 5. The middle panel shows CO J = 10−9 ( × ), CO J = 16 − 15 (stars) and in the upper panel: SO (13₁₃ − 12₁₂) 559.3 and SO (13₁₄ − 12₁₃) 560.2 GHz (triangles) and SO₂ (21_6,16 − 21_5,17) 558.4 and SO₂ (37_1,37 − 36_0,36) 659.4 GHz (squares).