The purpose of this paper is to develop some concepts for the mechanisms of emission formation during the combustion of liquid fuel sprays injected in swirling air. An emphasis is made on finely dispersed sprays used in open chamber diesel engines. The emissions studied are the unburned hydrocarbons, carbon monoxide, aldehydes, smoke particulates, and oxides of nitrogen.The spray is considered to be composed of a group of droplets of different sizes. The behavior of these droplets is determined by studying a mathematical model for droplet evaporation and ignition. The spray is then divided into regions, depending on the mechanism of combustion in each region. The emissions formed in each region are examined.The concepts developed for the formation of the different emissions in the spray are used for a qualitative analysis of some engine experimental data. These data are for the effect of the operating variables on the emission concentration in the exhaust of open chamber diesel engines. In these engines the fuel is injected in swirling air.