Because of the recent requirement to calibrate PM mass measurement devices using the NIOSH 5040 method, the need to produce repeatable soot characteristics and characterize the soot volume fraction using the Sunset OC/EC method has reappeared. The assumption is that the NIOSH 5040 method is highly reliable, precise, and accurate may be challenged. Moreover, CAST 13 burner soot or diffusion flame soot is known to have significantly different characteristics (volatile content, morphology, aggregate and primary particle size, graphitic characteristics, etc.). Thus, the response of the different PM mass measurement methods and especially LII need to be evaluated under these conditions. One primary challenge is to generate soot with characteristics similar to gas turbine soot. A further challenge is to ascertain what the relevant characteristics might be and then reproduce them in a concise and repeatable manner.