affects the following evolution of the star. This behaviour is as in the computations by Fujimoto and coworkers. We note that in this model experiencing a H-flash the amount of H ingested during the HEFM phase is $6.5\times10^{-4}\,M_\odot$.

![(a) The development of the different convective zones – indicated by shaded areas – as a function of time in our standard model. The solid and dashed lines represent the mass shells of maximum energy release by H- resp. He-burning. (b) The evolution of $L_{\rm H}$ (solid) and $L_{\rm
He}$ (dashed line) of the same model.\[fig4\]](fig4.eps){width="\columnwidth"}

The evolution of the convective zones during the major He core flash is shown in Fig. \[fig4\]. The single HECZ separates into two zones soon after the ingestion of H, because two burning shells are developing [an exhaustive description of this process can be found in @HIF90].

This behaviour is in agreement with the computations performed by @HIF90, although the treatment of the driving mechanism, the CNO-burning, is different: Hollowell and coworkers assumed that the abundances of isotopes involved in the CNO-cycle are locally in equilibrium, and that all of the energy from the CN-chain is released whenever a proton is captured on $^{12}$C, whereas we 