The dynamics of pressure-induced phase separation (PIPS) is important to processes that use near-critical or supercritical fluids. In this study, controlled pressure quench experiments were conducted in a 5 wt % solution of poly(dimethylsiloxane) (M-w = 93 700; M-w/M-n = 2.99)in supercritical carbon dioxide to determine the demixing pressures and its dependence on the rate of pressure change. Pressure quench rates were changed from extremely slow (ca. 0.008 MPa/s) to extremely rapid (ca. 500 MPa/s), and the system behavior was documented by real time recording of the changed in the transmitted light intensity, temperature, and pressure during the quench using a specially designed experimental system. The experiments were conducted on both the lower and the upper critical solution temperature (LCST and UCST) branches of the liquid-liquid-phase separation boundary. Apparent demixing pressures strongly depend on the rate and the depth of the pressure quench imposed and shift; to significantly higher pressures with an increase in the rate of quench if the initial temperature of the homogeneous solution is in the range where the system behavior is of the UCST type. The opposite is observed if the initial temperature is in the range where the system behavior is of the LCST type, and the demixing pressures shift to lower values, These are explained in terms of the actual pressure-temperature path the system follows because of significant cooling effects that accompany deep quenches.