Here’s one source: https://www.fema.gov/media-library-data/20130726-1622-20490-8811/nuclearfactsheet_final.txt https://www.fema.gov/media-library-data/20130726-

Here’s one source: https://www.fema.gov/media-library-data/20130726-1622-20490-8811/nuclearfactsheet_final.txt https://www.fema.gov/media-library-data/20130726-1622-20490-... The idea is to get away from an area where particles can collect (like the ground). They seem to be saying that you wouldn’t want to choose a floor with a balcony, for instance.