Alabama requires new K-12 schools to have shelters and a similar requirement is moving through the Illinois legislature. It is expected to pass, say sources.

Commercial-building safe rooms are not required and are not common. "It takes space and money—both items a business would rather use in other ways," says Chris Ramseyer, director of the Fears Structural Engineering Laboratory at the University of Oklahoma, Norman. Ramseyer led the 34-person investigation that influenced Moore's revised code.

Unregulated Shelter Makers

Since 2000, shortly after the FEMA 320 shelter standard was published, NSSA has tried to bring guidance to unregulated safe-room manufacturing, says Kiesling. But, currently, only 15% of all shelter makers are NSSA members.