The paper discusses the chemical structures of three common home heating fuels: wood, coal, and No. 2 fuel oil. GC and GC/MS data are then presented which demonstrate how the thermal destruction of each fuel results in the production of a characteristic group of organic 'fingerprint' compounds. For wood, where the chief structural element is lignin polymer, they are methoxy benzenes, methoxy phenols, and alkyl bezenes. For coal, where the polymer contains more fused-ring structures, the chief products are fused-ring aromatics with structures of three or more rings, benzothiophenes, and to a lesser extent methyl-substituted phenols. For oil, the chief byproducts are unburned droplets of the oil. The paper concludes with a brief discussion of how these fingerprints can be used as apportionment guides in complex airsheds.