“…Note that since the conditional means 365 are presented as a function of temperature, the shift to unity Lewis number behaviour is compounded by the thickening of the preheat zone presented in section 3.4. We argue that this shift in chemical composition is actually the beginning of the transition to distributed burning (see [15,16,9] and the references therein 370 for a detailed examination of the transition to distributed burning in supernova flames, lean premixed hydrogen, and larger hydrocarbons, respectively; other relevant studies include [21,22,10,11,23,24,25]). Distributed burning is the limiting behaviour when turbulent mixing dominates species and thermal diffusion; all fluid parcels are advected together, and the associated turbulent 375 diffusion dominates the molecular diffusion (and consequentially any changes in equivalence ratio) in this regime.…”