This paper presents an experimental and numerical study of heat flux and flame heights from fires generated in single burning item (SBI) tests. Thin steel plate probes were developed, as an inexpensive and reliable alternative to heat flux gauges, to measure the surface heat flux, whilst flame heights were determined by analyzing the instantaneous images extracted from the videos of the experiments by a CCD camera. Experimental results obtained at different heat release rates were subsequently used to assess the accuracy of the computational fluid dynamics (CFD) code, Fire dynamics simulator (FDS, V4.07). Simulation results indicated that though predicting reasonably flame heights FDS underpredicts significantly the surface heat flux at higher heat release rates. Consequently, a sensitivity study of the parameters used in the radiation and soot models in FDS was conducted.