The major requirement of civil defense effort must be to limit damage from large nuclear attacks and lay a base for the earliest possible national recovery. Therefore, assumptions must be developed as to the characteristics and scope of possible attacks.

During the National Shelter Survey, in which existing buildings were examined and evaluated for fallout protection, over 104 million adequate fallout shelter spaces were found. All buildings have shielded areas, affording some degree of protection. The basic protection can be enhanced in future building construction without appreciably increasing the cost or adversely affecting the esthetics and function for normal use.