In light of the nuclear situation in Japan I have decide to post some information on sheltering as a protection from radiation. At this time I do not expect radiation to become a problem in the United States. But in the eventuality that there is a worst case disaster this information could save your life. The attached diagram gives you an idea of the protection factors of various types of construction. The numbers in the various spaces indicate the protection factor, for example the number 3 shows that the radiation would be reduced to a 1/3, the number 10 to 1/10. You will notice that the average wood frame home gives inadequate protection protection. It is a good idea to survey your neighborhood and find the best protection or adequate shelter.
‘Adequate shelter’ is defined as shelter that protects against acute radiation effects, and significantly reduces radiation dose to occupants during an extended period. The adequacy of shelter is a function of initial radiation dose rates when fallout arrives and the dose rate reduction afforded by the structure. A shelter far from the radiation source may be adequate even if it provides little shielding, whereas the same shelter close into the radiation source may not be adequate. The primary risk from nuclear fallout is penetrating radiation that needs to be reduced as much as possible by shielding using dense building material and increased distance from deposited fallout, including on roofs that may be afforded by large buildings. Cars and other vehicles are not adequate shelters because they lack good shielding material. Good shielding materials include concrete, brick, stone and earth, while wood, drywall, and thin sheet metal provide minimal shielding. Basements and large concrete structures are good examples of adequate shelter. Large buildings can have thick walls of concrete or brick, but also provide the benefit of increased distance from deposited fallout materials when people gather away from exterior walls. This distance from exterior walls and roofs can substantially reduce radiation dose to those sheltering.
Shelters such as houses with basements, large multi-story structures, and parking garages, or tunnels, can generally reduce doses from fallout by a factor of 10 or more. These structures would generally provide adequate shelter, and individuals with ready access to these structures would protect themselves effectively even where initial unshielded fallout dose rates would result in lethal radiation dose levels.