Strap on a biohazard sign and put on there that containment suits are needed to enter (authorized personnel only - 60 min. max exposure time - hazard suit required) and you'll keep everyone out I bet. And fire fighters would still go in if necessary. Not sure how legal that is.... <img src="/images/graemlins/grin.gif" alt="" />

Foot thick steel reinforced concrete walls, roof and floor, no windows and solid steel door with frame embedded in the concrete with multiple industrial locks will help (Ving or Medeco high security....)