  A detailed discussion of recent results obtained within the hadron resonance
gas model with the multi-component hard core repulsion is presented. Among them
there are the adiabatic chemical freeze-out criterion, the concept of separate
chemical freeze-out of strange particles and the effects of enhancement and
sharpening of wide resonances and quark gluon bags occurring in a thermal
medium. These findings are discussed in order to strengthen the planned
heavy-ion collision experimental programs at low collision energies. We argue,
that due to found effects, at the center of mass collision energy 4-8 GeV the
quark gluon bags may appear directly or in decays as new heavy resonances with
the narrow width of about 50-150 MeV and with the mass above 2.5 GeV.
