Vaporization of liquid O-2 droplet in quiescent high-temperature and high-pressure H-2 gas is numerically investigated. Classical thermodynamic modeling of high pressure mixtures allows us to study the transition from subcritical to supercritical vaporization regime. It is observed that subcritical vaporization can be obtained up to pressures several times the oxygen critical pressure. Respective domain of both regimes is determined vs temperature and pressure. Border region corresponds to minimum value of droplet lifetime. This results from two cooperative phenomena : transient effect and thermodynamic property of mixtures. Sensitivity analysis additionally shows that state of art in dense fluid transport modeling yields results that should be considered accurate only as far as orders df magnitude are concerned.