This is a frustratingly lightly covered topic in all EMS training. I've been through EMT, and paramedic training and the NREMT gets you in the habit of doing the 10 second "BSI scene is safe" statement at the beginning without really teaching you to think critically about the safety of a scene. There are so many important pieces to scene safety from obvious physical hazards such as fire, weather, electrical hazards, and terrain concerns to the patient and other bystanders who can also present safety risks based on their mental state, physical state, and accessibility. Firearms and other weapons also present concerns not only overtly, but those that concealed carry can pose to provider and patient if not properly secured or set aside. Also scene safety isn't static it is a dynamic attribute that changes over time. Constant situational awareness is your primary tool in maintaining a high level of scene safety.