ABSTRACT In this paper the calculation of critical events in a fire situation defined as time for smoke logging and flashover is shown using two different fire models. Two models were used, a revised DFPA version of the simple model ASETB and the more complex model DSLAYV. Both of these are single-room models. They assume near-floor-elevation leakage and they have a capability for simulating the effect of ceiling ventilation to the outside ambient. In using the two models, the difference in calculated times is never larger than 15 % showing that ASETB works well as an engineering tool. The error which occurs when you are using wrong description of the fire growth is much larger.