||FLASHCHAIN is a reaction mechanism for the rapid devolatilization of solid fuels. This paper illustrates how the theory was recently expanded to predict the complete distribution of all major devolatilization products for a variety of fuel types, including any kind of coal, biomass, and petroleum coke. Noncondensible gases are now resolved into the primary hydrocarbon species (CH4, C2H9, C2H4, C3H9, C3H8), HCN, Hi, H2S, H20, C02, and CO. Tars are characterized by their complete elemental compositions (C/H/O/N/S) and their molecular weight distributions. Chars are characterized by their complete elemental compositions (C/H/O/N/S) and their sizes and densities. The theory also predicts the partitioning of chlorine and alkali species (Na and K). This paper also introduces a mechanism to describe the secondary pyrolysis of the primary devolatilization products, as occurs naturally at elevated temperatures in all combustion and gasification systems. During secondary volatiles. the volatiles are radically transformed, with complete conversion of tar into soot and conversion of all gases into H2, CH4, C2H2, HCN, H2S, CO, C02, and H20.