a) The OMC-1 core C¹⁸O J = 3−2 to ¹³CO J = 3−2 integrated intensity ratio map (θ_HPBW = 20″) overlaid with the ¹²CO J = 6−5 contours (grey) as shown in Fig. 1. The black contour represents the C¹⁸O/¹³CO abundance ratio of 0.122 (60/490). b) The OMC-1 core C¹⁸O J = 3−2 to J = 6−5 integrated intensity ratio map (θ_HPBW = 20″) overlaid with the ¹²CO J = 6−5 contours as shown in Fig. 1. Black triangles mark the Orion Hot Core position.