A brief presentation of the computer model DSLAY1, which describes the smoke-filling process in a single enclosure, is first given in experimental results to show the agreement between theory and experiment. In the latter part of the paper computed results are presented for areas where the model has been used for different fire engineering applications. The main purpose is to show that zone models like DSLAY1 are useful tools to predict the heat and smoke conditions in single enclosures as a result of growing fires. DSLAY1 is an interactive computer program. The user converses with the program via a terminal connected to the computer. The dialogue is governed by commands adapted to the concepts of the user.