In an average year, 800 tornadoes are reported nationwide, resulting in 80 deaths and more than 1,500 injuries. A safe room, which is a hardened structure specifically designed to meet FEMA criteria and provide "near-absolute protection" in extreme weather events, can survive winds as high as 250 miles per hour. It can be an interior room, space within a building or an entirely separate structure designed to protect occupants for events that normally last approximately two hours.
For the purposes of this program, the term "safe room" will include a prefabricated above- or below-ground residential shelter that meets or exceeds guidelines stated in the most recent versions of FEMA Publications 320 (Taking Shelter from the Storm) and FEMA 361 (Design and Construction Criteria for Community Safe Rooms), as well as ICC 500 (Standards for the Design and Construction of Storm Shelters).
FEMA 320 vs. FEMA 361
FEMA 320 provides guidance specifically aimed at homeowners, builders and contractors.