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.