Incorrect
Wrong—the Atomic bomb wasn’t used until the very end of WWII and fallout shelters did not become popular until the Cold War!
This U.S. Department of Defense (DoD) FS-1-series fallout shelter sign is 14 by 20 inches and made from aluminum. With a flat black and reflective yellow paint, the signs were posted on the exterior of buildings in order to identify sites that could be used by the public for shelter during a nuclear attack. The production of the signs began in the early 1960s and the iconic yellow-and-black symbol became inextricably associated with the Cold War era.