Industrial automation systems must comply with functional safety standards to protect humans, the environment and investments from the effects of hazardous events. Protection from cyber attacks is also required. Two industrial standards – IEC 61511 (Functional Safety – Safety instrumented systems for the process industry sector) and IEC 62443 (Security for industrial automation and control systems) guide development of the needed measures. The result is a Security Environment (for Safety) which describes all measures to be taken to ensure secure operation of a dedicated technical Safety system. The rules for safe, secure and economic setup of the Security Environment include: 1) making the perimeter protection as strong and “short” as possible, 2) making the functional units as resilient as possible and 3) limiting the interaction across the perimeters of the security zone(s).