If the word 'uncertainty' sounds extremely boring to you, this episode will prove you wrong. I have invited David Morrisset from the University of Edinburgh to discuss his research on the subject. Whereas in fact David is establishing standard deviations, means and other statistical means of quantifying uncertainty in core fire measurements, the really impactful and important part of his research is on explaining WHY those uncertainties are there. Through physical explanation of processes happening in fire we may grasp a really good understanding why two HRR-time curves of the same object burned in the same lab, in the same way may be so vastly different.These findings are fundamental for practical fire engineering. The establishment of design fires and their relation to the experiments is discussed in depth. We also talk about how we could establish better design fires for future engineering practice.Some excellent further reading:Repeat Fire Tests of Upholstered Furniture: Variability and Experimental Observations - the upholstered chair paperStatistical uncertainty in bench-scale flammability tests - the PMMA paper