This document gives guidelines whose primary focus is the assessment of the adverse environmental impact of fire effluents, including those from fires occurring in commercial and domestic premises, unenclosed commercial sites, industrial and agricultural sites, as well as those involving road, rail and maritime transport systems. It is not applicable to direct acute toxicity issues or wildland fires, which are covered by other existing ISO standards. It is intended to serve as a tool for the development of standard protocols for a) the assessment of local and remote adverse environmental impacts of fires, and the definition of appropriate preventive measures, b) post-fire analyses to identify the nature and extent of the adverse environmental impacts of fires, and c) the collection of relevant data for use in environmental fire hazard assessments. This document is intended as an umbrella document to set the scene concerning what should be considered when determining the environmental impact of fires. It is not a comprehensive catalogue of methods and models defining how to determine the environmental impact of fires, intended to be addressed by other parts of ISO 26367. This document is principally intended for use by firefighters and investigators, building owners and managers, storage facility operators, materials and product manufacturers, insurance providers, environmental regulatory authorities, civil defence organizations and public health authorities.