The way that a wildland fire burns and behaves, and the difficulty of controlling it, are closely related to the manner and rate of heat transfer. The speed with which fire spreads, for example, depends greatly on how quickly sufficient heat for ignition can be transferred to unburned fuel around the fire. And control of a wildland fire hinges on preventing or reducing heat transfer, reducing the heat available for transfer, or modifying the fuel so that more heat is needed for ignition and pyrolysis than is available. Heat can be transferred from one point to another in three ways-by conduction, by radiation, or by convection. Parts 1 and 2 of the series, the nature of heat and the transfer of heat by conduction were examined. Here we discuss radiation and heat transfer by radiation. The level of difficulty of the treatment of topics in these publications varies, as signaled by the color of the cover: the blue cover group is generally elementary and the yellow cover group is intermediate.