The scientific investigative techniques used to develop fact-based opinions on incident origin, cause, responsibility, prevention, and the potential damage and injuries in such circumstances are outlined in NFPA 921, Guide for Fire and Explosion Investigations. The Organization of Scientific Area Committees (OSAC), a group of over 600 forensic science professionals and specialists, recommends NFPA 921 as the consensus forensic science reference for fire investigations. Additional guidelines regarding an investigator’s opinions, confirmation bias, and expressions of certainty are included in the 2024 edition. Other changes include the relocation of all fire effects on electrical systems and components to Chapter 6 and the effect of suppression activities on fire ventilation and flow path that are distant from the area of origin.