A fluorescence monitoring system was used to measure gaseous sulfur dioxide at Taoyuan Agricultural Farm. A gas-diluting system and gas chromatograph equipped with a sulfur chemiluminescence detector used to audit the accuracy of diluted sulfur dioxide are described. The accuracy was -8% and -2%, respectively, for the preparation of 10 and 50 ppb SO2 standard gas. The pattern of variation of SO2 concentration at Taoyuan Agricultural Farm is reported. In summer at Taoyuan Agricultural Farm, the concentration of SO2 varied with a pattern of night concentration (15-20 ppb) greater than that in the afternoon (0-2 ppb). Computer-analyzed wind trajectories in Taiwan for this pattern are reported.