Since the thermal radiation of large-scale fires can be a hazard to surrounding buildings, there is a need for suitable models to describe the thermal radiation of these fires. With the presented radiation model OSRAMO II, which is exptl. validated, it is possible to calc. the mean surface emissive power of pool fires with pool diams. 8 m ? d? 25 m. Direct numerical simulations of a small-scale ethylene pool fire show that the periodical rise of vortex structures like soot parcels and hot spots has a major influence on the temporal variation of flame temp., soot vol. fraction and vol. emissive power. Furthermore the modeling of a large-scale kerosene pool fire shows a time depending temp. field due to the periodical rise of vortices.