ICC-500, ICC/NSSA Standard on the Design and Construction of Storm Shelters, establishesMINIMUM REQUIREMENTS for structures and spaces designated as hurricane, tornado, or combination shelters. The standard addresses the design of such shelters from the perspective of the structural requirements for high wind conditions and addresses minimum requirements for the interior environment during a storm event.
Scoping provisions mandate the construction of complying storm shelters in critical emergency operations facilities where such facilities are located in geographical areas where the shelter design wind speed is at its highest: 250 miles per hour. This geographical area, which includes most of the Interior Plains region of the United States, is identified in detail in ICC 500.
Critical facilities, such as emergency operations centers, fire and police stations, and buildings with similar functions, are essential for the delivery of vital services or the protection of a community. It is important to protect the occupants of such critical facilities struck by tornadoes, as well as to maintain continuity of operations for those facilities. Emergency operations facilities, as well as police and fire rescue facilities, are crucial to disaster response because an interruption in their operation as a result of building equipment failure may prevent rescue operations, evacuation, assistance delivery, or general maintenance of law and order, which can have serious consequences for the community after a storm event.
Most Group E educational occupancies must also be provided with complying storm shelters under the same criteria. Due to unpredictable and often very short tornado warning time, there are many high-wind events where it is unfeasible to evacuate school buildings. Therefore, it is very important that refuge areas be provided that are capable of providing a near-absolute level of protection for the vulnerable individuals. The minimum required shelter capacity can be provided in the educational building served, in an adjacent building or buildings, or in a combination of buildings. Where a remote storm shelter is required to provide the required capacity, the entry door of the shelter must be no more than 1,000 feet (305 m) of travel distance from an exterior door of the building served. Where the building served is a Group E occupancy, additional criteria addressing the determination of the minimum required capacity of the storm shelter(s) is provided.