Experiments are conducted on a laboratory-scale fixed bed combustor. This article discusses some of the data analysis methodologies that define the onset of steady state conditions, which are widely reported in the literature but poorly defined. The effects of using different methods to determine the onset of the steady state performance, and to correct thermocouple data so as to account for radiative effects, are also presented. Results show that using a combination of CO and NO emissions with free-board temperatures (at multiple axial positions) is more effective than other emissions, using temperatures (only) or the fuel burning rate (kg m(-2) s(-1)). An important indicator is to analyze the percentile deviation of temperatures and emissions, compared to only using the time evolution of these variables. To characterize the significance of correcting thermocouple data for radiative (wall) losses, two numerical models (aspirated and bare bead) were compared. Radiative effects on thermocouples were found to be most prominent nearer to the downstream secondary air inlet due to the cooler wall temperature. Due to the likely radiative effects from freeboard deflectors, the sensitivity of these outcomes to the presence of downstream deflectors is also presented.