  The importance of NCO chain on the onset of the He-flash in degenerate
physical conditions has been reevaluated. We find that low-mass, metal-rich (Z
$\ge$ 0.001) structures climbing the Red Giant Branch do never attain the
physical conditions suitable for the onset of this chain, while at lower
metallicities the energy contribution provided by NCO reaction is too low to
affect the onset of the central He-flash. At the same time, our evolutionary
models suggest that for a Carbon-Oxygen White Dwarf of mass M_{WD}=0.6 M_sun
accreting He-rich matter, directly or as a by-product of an overlying H-burning
shell, at rates suitable for a dynamical He-flash, the NCO energy contribution
is not able to keep hot enough the He-shell and in turn to avoid the occurrence
of a strong electron degeneracy and the ensuing final explosion.
