Before a wildland fire can start, heat must be transferred from a firebrand to the fuel. Then heat must be transferred from the fuel surface to deeper layers if the fire is to continue to burn. Finally, heat must be transferred to surrounding unburned fuel if the fire is to spread. And decreasing or eliminating heat transfer is about the only way we have of controlling and extinguishing a fire. Heat transfer is hence an essential part of wildland fire and fire control. Heat can be transferred in three ways-by conduction, by radiation, and by convection. All three methods are usually operating at the same time in a wildland fire. In Parts 2, 3, and 4 of this series, we explored the role of conduction in the combustion process and in fire control, and the characteristics of heat transfer by radiation. Now we will examine heat transfer by radiation in relation to fire behavior, fire control, and firefighting safety. 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.