A procedure for synthesizing safety controllers for pervasive computing environments is described. Control-theoretic techniques are used in the synthesis. We describe the notions of Connected Spaces and Digital Device Manuals for modeling pervasive computing environments and devices, respectively. The safety requirements for the environment are specified as a set of safety policies. The safety policies are enforced by the safety controller. The notions of policy relaxation cost of the safety policies and safety criticality ranking of the devices are novel to this work. An experimental evaluation of the synthesis procedure is presented. Results show that the synthesis procedure scales linearly with respect to the density of the set of policies.