Sulfur species are critical contaminants in ammonia gas. They can cause high-temperature sulfidation of metals, form aggressive complexes with other elements, or react subsequently in processes where the ammonia gas is used. The concentration of such impurities tends to be very low, but they may not exceed critical levels of 0.5 mg/L. Although this level is very close to the system blank of the Combustion IC system, the setup can be used to prove that such critical limits are not exceeded.