In my story, my 1940s-era main character is due to be married before an atomic bomb hits. Her home is still standing after the blast. Her wedding dress was kept in her second story bedroom.
18 years later, she gives her unused dress to another woman who needs one for her wedding.
However, I'm not sure if the dress would be safe to wear. I assume that it is because the house was still standing and the walls of the home would prevent the dress from fallout. However, the sites seem to think that the shelter one would need to protect against a blast needs to be air-tight, which this house would not be.
If the dress would NOT be safe to wear, how could my main character logically store the dress prior to the blast that would make it safe to wear 18 years later? It can't be locked up somewhere because another character needs to see the dress prior to the blast and remark on it.