The paper discusses the use of a refactory-lined, natural gas furnace to study the fuel-rich sulfur capture reactions of calcium sorbents under typical combustion conditions. The fuel-rich sulfur species hydrogen sulfide and carbonyl sulfide were monitored in a nearly continuous fashion using a gas chromatograph equiped with a flame photometric detector and an automatic system that sampled every 30 seconds. Below the fuel-rich zone, 25% excess air was added, and the ultimate fuel-lean capture was simultaneously measured using a continuous sulfur dioxide monitor. Under fuel-rich conditions, high levels of sulfur capture were obtained, and calcium utilization increased with sulfur concentration. The ultimate lean capture was found to be weakly dependent on sulfur concentration and independent of the sulfur capture level obtained in the fuel-rich zone.