NORAD S-Series bomb shelters provide a Total Rems in Shelter (TRS) of less than 5 rems at the shelter design pressure of 10 psi. The TRS rating includes radiation entering the shelter from air pipes, entranceways and overhead. Radiation doses used for this rating are described in Principles of Protection. As we say on our Blast Shelters page (Point Z is where the entrance meets the hull):

“To be a ‘blast shelter’ the structure must have a TRS or Total Rems in Shelter rating. The TRS indicates how many rems the shelter occupants will receive at specific distances from ground zero from overhead, entranceways and air ducts. NORAD S-Series Underground Shelters have a TRS of 4-10. Shelterists will receive a maximum of 2 rems radiation at Point Z during a bomb blast creating 10 psi over pressure (see Point Z image below). The TRS measures all forms of radiation from all shelter exposure points.”