Correlation between the observed I(HCN)∕I(HNC) (this work) and measurements of the gas kinetic temperatures derived using NH₃ observations(Friesen et al. 2017) with reliable temperature estimates (i.e. δT_K∕T_K ≤ 50%; grey crosses). These positions with good temperature estimates (i.e. δT_K∕T_K ≤ 5%) are colour-coded according to their total H41α intensity (see Fig. 1). A systematic increase in the gas kinetic temperatures in Orion is clearly visible in positions with strong I(H41α) emission, which denotes their proximity to the ONC. The empirical linear fit of each of the low- (solid red line) and high-(dotted red line) temperature regimes are indicated in the plot (see Sect. 4).