This guidance provides Assessors with advice on hazards from chemical warehouses based on current knowledge. It has to be clearly understood at the outset that some of the technical issues involved in warehouse fires are complex and the aim of most assessments will be a reasonable, physically consistent but approximate treatment. Research continues in the areas of: fire behaviour of chemical commodities, production of toxic species, structural response and effects of emissions on human populations and the environment. Parts of this guidance may be superseded as new information becomes available.