A series of experiments were carried out to determine if the condensation section of an organic gas capture and recovery system was operating at VLE. The vapor phase concentration of isobutane inside a chilled pressure vessel was measured at 563-1273 kPa absolute (81.7-184.7 psia) and -6°-20.1°C. These pressures and temperatures corresponded to equilibrium vapor phase concentrations of 10.9 to 38.6 vol % isobutane in the condenser. The measured isobutane concentrations agreed with the theoretical equilibrium isobutane concentrations with an absolute relative difference of < 4.9% for the discrete measurements. Modeling vapor-liquid equilibrium in the chilled pressure vessel allowed the gas phase concentration above the condensed organic gas to be maintained by controlling the temperature and pressure in the condensation system. This is an abstract of a paper presented at the 103rd AWMA Annual Conference and Exhibition (Calgary, Alberta, Canada 6/22-25/2010).