This Code provides procedures for the conduct and reporting of performance tests of flue gas desulfurization systems. The performance of a flue gas desulfurization system (FGDS) is defined to be the characterization of inputs and outputs that may include, but is not necessarily limited to, the following: (a) Percent SO removal (%R); (b) Reagent Ratio (RR1 or RRR); (c) Energy/power consumption; (d) Water consumption and characterization; (e) Reagent consumption and characterization; (f) Waste/by product production and characterization; and (g) Availability and Reliability. Availability and reliability of the FGDS are outside the scope of this Code. This Code also contains supplementary information on (a) Types of FGDS; (b) PTC 40 Test Method; (c) FGD data determination Forms; (d) Quantity measurement of solid waste; and (e) Example application.