The effect of thermal radiation on unprotected human beings is likely to be very serious, producing flash burns over large areas of the body. However, the Hiroshima and Nagasaki bombings demonstrated that once the victim is beyond the radius at which light-colored fabrics are directly ignited, even simple precautions can greatly reduce the extent and seriousness of thermal injuries. Many examples exist of people severely burned on their faces and arms, but unburned beneath even a thin shirt or blouse. Thermal effects on structures are equally complex. Films of tests conducted in Nevada in the 1950 s confirm that at the extreme distance at which wood-frame houses can be ignited by lower yield weapons, the buildings are blown apart seconds later by the blast wave, while structures which survive the blast do not ignite after the blast.
Tests conducted in the Pacific using megaton-class weapons show the opposite effect.
Secondary fires started by broken gas mains, electrical short circuits, etc., can considerably amplify the overall effects of a nuclear detonation.