In biomass gasification plants and related research units, on-line analysis of noncondensable compounds (H-2, CO, CO2, CH4, and light hydrocarbons) and condensable compounds (water, tars, etc.) is desired. Long-duration on-line measurements are often a challenging task, because blocking of the sampling lines has to be avoided and because some analytical equipment do not tolerate certain components of these streams. A continuous liquid-quench sampling system has been successfully employed to sample these gas streams and prepare them for on-line measurement. In comparison to other systems, it promotes long-duration measurements with high time resolution over a wide concentration range with little man-hour requirements. In this work, the sampling system is described in detail for the first time and its performance is investigated regarding the sampling of noncondensable compounds. On the basis of experimental observations, optimal operational parameters are suggested to minimize the measurement bias.