"This joint FCDA-AEC [Federal Civil Defense Administration-Atomic Energy Commission] project was conducted to check the adequacy of several proposed home shelter designs. Underground earth-covered shelters were exposed to a 16.4-kt, 300-ft tower shot at ranges of 1230 ft (one), 1450 ft (one), 1800 ft (five), and 3500 ft (one). Two types of basement shelters were constructed in each of the test houses at 3500 and 7500 ft (Project 21.2). Instrumentation was by gamma-radiation badges, paraffin cubes, and nylon swatches. Attempts were made to measure permanent deflections of concrete roof slabs. Mannequins were placed in several shelters for purposes of demonstration and observation of blast-caused movement. A weighted mannequin in the underground shelter at 1230 ft was broken in half; an unweighted one (child size) was thrown to the floor. All other mannequins remained in place, undamaged. Paraffin cubes and nylon swatches showed no evidence of thermal damage. Fallout conditions made it impossible to determine initial gamma-radiation quantities. There was no cracking or permanent deflection of the concrete roof slabs. Except for a wood-covered, trench type shelter, which partially failed because of faulty construction, the shelters showed no blast damage. Thermal energy entering the shelters probably would not have caused skin burns to human occupants. Adequacy of the shelters under full design loads could not be determined because pressures were lower than expected, but the shelter designs were structurally acceptable under test pressures received. Future tests are required under higher pressures. The basement shelters should be tested under masonry debris loads."
United Stated Federal Emergency Management Agency, Learning Resource Center: http://www.lrc.fema.gov/