¹³CO mm-wavelength transitions in OH 231.8+4.2. We labelled the different spectral features in the ¹³CO profiles as I1–I5 to identify them with the corresponding regions/clumps of CO-outflow where the emission features mainly arise (see Fig. 1). Top panel: ¹³CO J = 1–0 spectrum is also plotted using a larger T_mb scale for an improved view of the weak broad wings.