Take cover as quickly as you can, below ground if possible, and stay there until instructed to do otherwise.They can be any protected space, provided that the walls and roof are thick and dense enough to absorb the radiation given off by fallout particles. Fallout shelters do not need to be specially constructed for protecting against fallout.But even a blast shelter cannot withstand a direct hit from a nuclear explosion. Blast shelters are specifically constructed to offer some protection against blast pressure, initial radiation, heat, and fi re.The following describes the two kinds of shelters: There are two kinds of shelters-blast and fallout. Taking shelter during a nuclear blast is absolutely necessary. What to do in the event of a nuclear explosion During periods of increased threat, increase your disaster supplies to be adequate for up to two weeks.If you live in an apartment building or high-rise, talk to the manager about the safest place in the building for sheltering and about providing for building occupants until it is safe to go out.These places would include basements or the windowless center area of middle floors in high-rise buildings, as well as subways and tunnels. If none have been designated, make your own list of potential shelters near your home, workplace, and school. Find out from officials if any public buildings in your community have been designated as fallout shelters.

To prepare for a nuclear blast, you should do the following: Remember that any protection, however temporary, is better than none at all, and the more shielding, distance, and time you can take advantage of, the better. Radioactive fallout poses the greatest threat to people during the first two weeks, by which time it has declined to about 1 percent of its initial radiation level.

In time, you will be able to leave the fallout shelter.

Time - fallout radiation loses its intensity fairly rapidly.

Shielding - the heavier and denser the materials-thick walls, concrete, bricks, books and earth-between you and the fallout particles, the better.

Flat roofs collect fallout particles so the top floor is not a good choice, nor is a floor adjacent to a neighboring flat roof. A floor near the middle of high-rise may be better, depending on what is nearby at that level on which significant fallout particles would collect. An underground area such as a home or office building basement offers more protection than the first floor of a building.

Distance - the more distance between you and the fallout particles, the better.

The three factors for protecting oneself from radiation and fallout are distance, shielding, and time.

Fallout shelter incident level