Comparison of the FUV radiation field strength, G₀ (upper panel), hydrogen nuclei density, n (middle panel), and the χ² value (lower panel) from fitting the Kaufman et al. (1999, 2006) PDR model to the [Cii] and F_TIR emission together with either the [Oi] 63 or 145 μm line emission, adjusted via the -based correction. The difference between the parameters are plotted against the logarithm of the TIR emission, and the coloured bins correspond to the schematic in Fig. 2. The quoted values are the overall scatter (σ) defined as the standard deviation of the difference (δ) between the PDR model parameters constrained with each [Oi] line.