Abstract: Apparati and methods for controlling the distribution of steam to a number of boilers, and for optimizing the performance of a steam boiler. The distribution of steam to the boilers is controlled by a master control system in communication with the boilers, steam subheaders, steam-flow sensors, a comparator module, a summer module, a main steam-supply header, and a pressure sensor in the main steam-supply header. The performance of an individual boiler is optimized by (a) maintaining a constant steam pressure in the boiler, (b) measuring the relative humidity of the air supply for fuel combustion, and (c) supplying and controlling the amount of steam to be mixed with the air supply to optimize the combustion process.