Which locations within the bomb shelter appear to offer the best protection against fallout? Sketch a bomb shelter floor plan and mark these locations.
The best protection is provided by getting as much mass as possible between you and the fallout. Walk through the bomb shelter and get an idea where the best protected areas might be. Usually, but not always, the areas having the least amount of daylight reaching them will provide the best protection.
Basements provide good protection from the sides if they are well below ground and there is earth all around, but they may not always provide good protection from “skyshine” or from radiation from fallout that has settled above the basement or on neighboring rooftops.
If the floors above the bomb shelter are made of solid concrete, they will be much more massive than floors of wood and will provide much better protection from overhead gamma radiation.
Similarly, walls of solid brick or concrete will provide better protection than walls of hollow concrete or cinder-block; these walls, in turn will provide better protection than walls of gypsum board (sheetrock) or plywood.
Tall buildings can provide good protection from gamma radiation in the inner rooms of floors that are at least four stories above the ground or surrounding rooftops. There should be at least three stories above the bomb shelter to provide protection from fallout on the roof. These locations do not provide blast protection and should not be used in areas less than 25 miles from a likely target for a nuclear weapon.
If we expect the gamma radiation from fallout to be reduced at a certain location by a factor of four from what the radiation level would be outside above a very large, flat, smooth, open area, covered with the same kind and amount of fallout, we say the Fallout Protection Factor (FPF) of the location is four. This factor is also called the Protection Factor (PF).
Some locations that are rated with a high protection factor, such as bomb shelters in upper levels of a skyscraper, may provide little protection against other nuclear weapons effects such as blast. A high FPF for a bomb shelter location only indicates good protection against gamma radiation from fallout.
Such a bomb shelter location may also, but not necessarily, provide protection against other nuclear weapons effects. The term FPF is used in this book instead of PF to indicate the protection provided by a bomb shelter location against gamma radiation from fallout.
Some FPF’s that might be possible in different locations in buildings are shown in the image above. Deep basements and buried bomb shelters have high FPF’s (1,000 and above). They provide good protection against gamma radiation from fallout in the locations indicated by dots in the drawing, but they provide little protection against blast.
The FPF’s indicated above and below-ground bomb shelters that are surrounded or partly surrounded by buildings. The first floors of houses and partially buried basements have low FPF’s and provide little protection against gamma radiation from fallout.
The next image is an example of a sketch of a floor plan of an apartment building. Two kinds of interior wall construction are indicated in the sketch, concrete block and wallboard, probably gypsum. The rooms have been named with letters of the alphabet. Room “G” looks like it would provide the highest FPF’s because it is surrounded by outside rooms and has walls of concrete block.