A general model is developed for predicting the generation rates of oxygen, fuel, and any other products of combustion of interest in rooms containing fires. The model is called the generalized global equivalence ratio model. It extends the steady state global equivalence ratio model established from steady-state data of several previous experimenting studies. After presenting the details, a concise algorithm is outlined for implementing the model in two-layer zone-type compartment fire model computer codes. With the algorithm in place, such codes could be used to simulate the distribution of proeducts of combustion in single or multi-room fire environments. In an example application, the model is used to simulate the time-dependent environment, including that of steady-state, in some of the above-metioned experimental studies. For arbitrary experimental conditions and under assumption of stoichiometric combustion, solutions for concentrations of products of combustions are obtained and presented. In one concise result, the solutions are used to predict the time-to- extinguishment of a burning methane fuel source embedded in an initially ambient-atmosphere upper layer.