Evaluated by four independent engineering firms, the FlatSafe Tornado Shelter respects every aspect of your safety and convenience, including in-home access. The extensive research and development of the FlatSafe Tornado Shelter addresses the fundamental components of a reliable tornado shelter. The most important considerations for a below grade shelter consist of proper ventilation, impact strength, corrosion control, buoyancy resistance, safe entry, and emergency egress.According to a National Storm Shelter Association (NSSA) Evaluator, Dr. James McDonald, a Professional Engineer, “The FlatSafe Tornado Shelter designs are well documented and well thought out”. Dr. McDonald also mentioned “The attention to detail is commendable”. In addition to the conclusions of a NSSA evaluator, Larry Tanner, a Professional Engineer and Research Associate at Texas Tech University, stated; “The Wind Engineering Research Center at Texas Tech University applauds your company’s efforts in providing a safe product for the consumer”.Transferable one-time, FlatSafe offers a 25 year corrosion warranty and is available before, during, and after the residential construction process. An Engineer’s structural analysis and drawings for architects, home builders, and permit offices are available upon request.