  Boost-invariant hadron production in high energy collisions occurs in
causally disconnected regions of finite space-time size. As a result, globally
conserved quantum numbers (charge, strangeness, baryon number) are conserved
locally in spatially restricted correlation clusters. Their size is determined
by two time scales: the equilibration time specifying the formation of a
quark-gluon plasma, and the hadronization time, specifying the onset of
confinement. The expected values for these scales provide the theoretical basis
for the suppression observed for strangeness production in elementary
interactions ($pp$, $e^+e^-$) below LHC energies. In contrast, the space-time
superposition of individual collisions in high energy heavy ion interactions
leads to higher energy densities, resulting in much later hadronization and
hence much larger hadronization volumes. This largely removes the causality
constraints and results in an ideal hadronic resonance gas in full chemical
equilibrium. In the present paper, we determine the collision energies needed
for that; we also estimate when $pp$ collisions reach comparable hadronization
volumes and thus determine when strangeness suppression should disappear there
as well.
