the usa civil defence fallout shelter sign yellow backdrop

backdrop background computer generated graphics illustrations usa united state states america american americans fallout nuclear symbol symbols sign signs civil defense defence three invert inverted triangle triangles triangular shelter shelters emergency emergencies enclosed enclose space spaces designated protect protection human humans extinct extinction genocide genocidal bomb bombs missile missiles launch launched ballistic ballistics press button detonate detonation explode explosion fusion radioactive material materials expose exposed exposure particles gamma ray rays radiation hazards thermal effect effects accident accidents disaster disasters