Shaft seals have a substantial impact on turbomachinery performance. Due to minimized friction and low leakage rates, mechanical dry gas seals outpace other shaft sealing technologies in terms of efficiency when it comes to sealing gases at elevated pressures. Therefore, dry gas seals are standard equipment for most centrifugal compressors nowadays. Even in some pump applications, they have shown significant advantages for sealing liquid media. Dry gas seals are an important tool to optimize supercritical carbon dioxide (sCO2) turbomachinery and therefore sCO2 power cycles to the desired levels of efficiency. The special characteristics of CO2 are challenging for the safe operation of dry gas seals in CO2 applications. E.g., we must avoid icing of CO2, related to the Joule-Thomson effect when expanding CO2 through the sealing gap, must be avoided. In addition, transitions between supercritical and liquid phase need to be carefully addressed. EagleBurgmann is a manufacturer of dry gas seals and has constructed a CO2 test loop for operating dry gas seals in a CO2 environment, covering all non-solid phase conditions, i.e. gaseous, supercritical, liquid and liquid-gas. Moreover, dry gas seal designs, especially dedicated to operation in sCO2 pumps and compressors have been developed. The paper shall give insight into the seal and test loop design, the test campaign and results.