It is shown that the radiative light emission from a coal boiler contains spectral information revealing the presence of sodium within the flame. Because sodium is a major contributor to fouling in low-rank coal power stations, a sodium analysis system has been developed based on this phenomenon. The analyzer is being trialed at a commercial power station over an extended period, with the response of the analyzer being correlated to station parameters such as coal quality, load, and mill availability. A normalization procedure has been adopted to reduce the analyzer＇s response to boiler temperature and load changes. Qualitative results to date indicate that the analyzer response can be related to the fouling properties of the coal.