O. Reg. 267/03, the "General" regulation made under the Nutrient Management Act, 2002, sets out an odour classification system for non-agricultural source materials (NASM) that are applied to agricultural land. This guide sets out the 3 methods that can be used to determine where a specific NASM fits within the odour classification system including historical data, comparative and empirical assessment and the professional judgment of ministry staff. The regulation prescribes setback distances from dwellings, residential areas and land with a commercial, community or institutional use based on odour categories and application method. The odour category also affects storage and handling requirements for OC3 NASM.