Before discussing the three general types of fallout, it is well
to call attention to the fact that a deep underground burst such as was
accomplished in Nevada in September 1957 is completely contained and
produces no surface or atmospheric contamination.
There are three different classes of fallout from tests, the relative abundance of which is determined by the nature of the weapon, its
yield, and the conditicns of detonation, particularly the altitude of
firing.
Local or near-in fallout occurs when the fireball of the bomb
touches or comes sufficiently close to the ground to draw up into the