Results are described of an investigation into the formation of pollutants in an ammonia-vapour combustion system that is part of the coking unit of Companhia Siderurgica de Tubarao, a Brazilian steel-manufacturing company. The work was motivated by the need to control the amounts of pollutants emitted by the combustion process. First, the procedures for determining the chemical compositions of ammonia vapour and the product gas are presented; then a kinetic model for the combustion system is described. The model allows determination of a) the concentration of generated pollutants, b) the conditions for initiation and termination of each product formation, c) the effects of temperature variation, d) the effects of air:fuel ratio, and e) the effects of secondary-air injection. The results from the model compared well with experimental data obtained in the field.