Describes a theoretical model for calculating thermochemical properties of the gaseous fuel that burns in the free flame at the edge of a spreading fire in fine forest fuels. Predicted properties are the heat of combustion, stoichiometric air/fuel mass ratio, mass-averaged temperature, and mass fraction of unburned fuel in the gas mixture emitted from the flame-producing zone. These variables depend upon readily determined intrinsic properties of the fuel, the fuel moisture content, fuel particle surface/volume ratio, particle mass density, and fuel loading. Numerical examples are given for several fuel types, exploring the sensitivity to moisture content, char fraction formed (an inherent property of the fuel that can be modified by fire retardants), and an energy-leakage fraction related to fuelbed opacity. All the equations are given in appendixes.