An inflatable fabric dome -- with a bit of construction technology -- can hold up to 800 people and should be resistant to an EF-5 tornado. It's being constructed at Smithville School in Mississippi. Once the fabric is inflated, insulation is added to the inside and then a rebar grid is tied to the inside of that. "It will look like a big bird cage for a little while, and then we spray concrete -- which is called shotcrete -- on the inside," said Randy South, president of South Industries, the company building the structure. "We embed that rebar and when the rebar is all embedded, we let the concrete cure for a little while, turn the fans off and you got a concrete building."

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