For the first 60 years of the 20th Century, criteria and methods based on the results of catastrophic events were used for the design of explosive facilities. The criteria and methods did not include a detailed or reliable quantitative basis for assessing the degree of protection afforded by the protective facility. In the late 1960's quantitative procedures were set forth in the first edition of the present manual, Structures to Resist the Effects of Accidental Explosions. The manual was based on extensive research and development programs which permitted a more reliable approach to current and future design requirements. Since the original publication of this manual, more extensive testing and development programs have taken place. This additional research was directed primarily towards materials other than reinforced concrete which was the principal construction material referenced in the initial version of the manual. An upgrade to the manual, describing new design techniques has become essential. Design methods in the proposed upgrade provide required structural protection.