The paper briefly reviews our scientific understanding of some of the better understood flammability properties such as ignitability, flame spread, and convective burning to illustrate the utility of practical test method apparatuses for evaluating flammability properties. We then discuss the essential role of flame radiation in control1ing hazardous scale burning rates and why we presently think that a fuel's classical smoke-point may indicate its radiative hazard. We then examine in more detail the soot radiation from small laminar flames to illustrate our emerging scientific understanding of flame radiation. Finally, we suggest a possible smoke-point radiation test apparatus suitable for solid fuels.