Blast shelter

A blast shelter is a place where people can go to protect themselves from bomb blasts. It differs from a fallout shelter, in that its main purpose is to protect from shock waves and overpressure instead of from radioactive precipitation, as a fallout shelter does. It is also possible for a shelter to protect from both blasts and fallout.

Blast shelters are a vital form of protection from nuclear attack and are employed in civil defense. There are above-ground, below-ground, dedicated, dual-purpose, and potential blast shelters. Dedicated blast shelters are built specifically for the purpose of blast protection (see bunker). Dual-purpose blast shelters are existing structures with blast-protective properties that have been modified to accommodate people seeking protection from blasts. Potential blast shelters are existing structures or geological features exhibiting blast-protective properties that have potential to be used for protection from blasts.

Blast shelters deflect the blast wave from nearby explosions to prevent ear and internal injuries to people sheltering in the bunker. While frame buildings collapse from as little as 3 psi (20 kPa) of overpressure, blast shelters are regularly constructed to survive several hundred psi. This substantially decreases the likelihood that a bomb can harm the structure.

The basic plan is to provide a structure that is very strong in compression. The actual strength specification must be done individually, based on the nature and probability of the threat. A typical specification for heavy civil defence shelter in Europe during the Cold war was an overhead explosion of a 500 kiloton weapon at the height of 500 meters. Such a weapon would be used to attack soft targets (factories, administrative centres, communications) in the area.

Only the most heavy bedrock-shelters would stand a chance of surviving. However, in the countryside or in a suburb, the likely distance to the explosion is much larger, as it is improbable that anyone would waste an expensive nuclear device on such targets. The most common purpose-built structure is a steel-reinforced concrete vault or arch buried or located in the basement of a house.

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Wikipedia