This handbook is written for radiation safety in shelters in areas that will not be affected by the primary nuclear weapons effects of blast, fire, and initial nuclear radiation. In a nuclear war, up to 90 percent of the land area of the 48 states of the United States could be covered with radioactive fallout that would deliver hazardous nuclear radiation to an unprotected person over a period of several days before decaying to much less hazardous levels. On the other hand, about 10-15 percent of the land area could be affected by primary nuclear weapons effects that would pose additional hazards to the population remaining there. In those areas, additional safety measures must be taken that are not described in this handbook. Nearly all the radiation safety measures and procedures described in this handbook will be useful in all shelters. The procedures for watching for fallout to arrive should not be followed in shelters that are less than 25 miles from a likely target for a nuclear weapon. At such locations, the possibility of other nuclear weapons effects such as blast and thermal radiation will place the Radiological Monitor (RM) following this procedure under greater risk than necessary.