 Inherent safety, also called primary prevention, consists in the elimination of a hazard. It is contrasted with secondary prevention that consists in reducing the risk associated with a hazard. For a simple example, consider a process in which inflammable materials are used. Inherent safety would consist in replacing them by non-inflammable materials. Secondary prevention would consist in removing or isolating sources of ignition and/or installing fire-extinguishing equipment. As this example shows, secondary prevention usually involves added-on safety equipment. The major reason to prefer inherent safety to secondary prevention is that as long as the hazard still exists, it can be realized by some unanticipated triggering event. Even with the best of control measures, if inflammable materials are present, some unforeseen chain of events can start a fire. 