[O I] luminosity at 63 μm as a function of the bolometric luminosity of the object. The black curve represents the best-fit result of the data with f(x) = 0.65 ⋅ x − 3.6 and χ² = 7.8. We show two additional lines which partially fit the data (in red) with f(x) = 0.94 ⋅ x −3.7, L_bol <17 L_⊙, and χ² = 3.5, and (in blue)with f(x) = 0.13 ⋅ x − 2.6, L_bol >17 L_⊙, and χ² = 3.2. We also show the best fit of Green et al. (2013a) with f(x) = 0.70 ⋅ x − 3.7 (in green). The data points that are indicated as upper limits (3σ) and EX Lup are not used to create the fits.