A skid mounted test facility has been built for determining conditions at which CO2 flashes from geothermal brines. The system has been checked and operated at one geothermal plant. It performed as designed. The equipment is designed to operate at temperatures and pressures typical of wells near Heber, California. (Nominally IS0°C and 300-500 psig). It has heat exchangers which can cool the brine to less than 70°C. (The cooling water is re-circulated after being cooled by a forced air heat exchanger). Breakout pressures can be determined for any temperature between 70°C and wellhead temperature