Gamification provides a prominent technique that can be used to provide Immersive Learning Environments (ILEs) for domains, where it is dangerous or expensive to learn in real environments. Especially industrial organizations (e.g., manufacturing, mining, construction) are a promising domain for implementing ILEs that combine gamification concepts with a pedagogical design to facilitate safety training under secure circumstances. Although there are design research studies that exemplify the utility of gamification of learning activities, or how to improve organizational safety training through gamification, there is a need to address how sustainable safe spaces can be designed for enhanced safety training in ILEs. Safe spaces are key elements of a successful safety training experience in ILEs as they provide safe and secure training environments, which in the physical world are typically considered too dangerous with high risk of injuring the training participants. This study reports findings from an ongoing DSR project that stresses the design of ILEs for sustainable safety training. Within the project, an artifact for immersive fire safety training in virtual reality has been designed, developed, and evaluated together with employees of a train operator company. The research responds to the need of producing design knowledge that moves beyond the highly contextualized designs principles that are particular for IVR applications. We use gamification concepts as a kernel theory for developing a mid-range theory of designing immersive virtual safety training environments.