The computer controlled FlexStream gas standards generating system blends calibration gas standards for trace sulfur compounds in food grade carbon dioxide. Permeation tubes add low ppb concentrations of typical sulfur species including COS, H2S, mercaptans directly to a controlled flow of purified, beverage grade CO2 to create trace concentration calibration standards. Residual background contamination in the CO2 matrix gas is compensated for by using the standard additions technique. Calibration is based on the known difference in sulfur compound concentration due to the addition from the permeation tubes. A secondary dilution feature gives ppt concentrations. Suitable for carbon dioxide quality assurance, laboratories, the food and beverage industry and pharmaceutical processing this unit has a front panel color touch screen, a permeation tube oven and Ethernet and serial RS-232 connectivity to an external computer.