This guide is intended as a reference for US users who may have reason to work with the system in the United States, where English units are primarily used. Keep in mind that the Canadian Forest Service has produced the definitive selection of reference publications and tools referenced below. The Canadian Forest Fire Danger Rating System (CFFDRS) was first conceived in 1968. The Fire Weather Index (FWI) system was developed and introduced across Canada in 1970. The Fire Behavior Prediction (FBP) system was introduced in 1984. The Fire Occurrence Prediction (FOP) system and Accessory Fuel Moisture system are still in development, with several regional modules operational at this time. Though this guide attempts to be faithful to the models embedded in CFFDRS, there are a number of adaptations to the standard depictions found in materials produced by the Canadian Forest Service.