What is the main reason occupied areas have higher design criteria in NFPA 13?

In NFPA 13, the primary reason that occupied areas have higher design criteria is due to the potential for higher fire risk associated with these spaces. Occupied areas typically contain people, materials, and equipment that can contribute to a fire's initiation and spread. As a result, the design and installation of sprinkler systems in these settings must account for the unique challenges posed by the presence of occupants and the types of activities occurring within those spaces.

For example, areas such as assembly halls, offices, and residential spaces often have furnishings and other combustibles that can increase the fire load. Additionally, the need to protect human life makes it imperative to provide adequate water discharge rates and coverage to effectively suppress fires in these environments. The specific design criteria, therefore, ensure that the sprinkler systems are adequately equipped to handle the increased risk and potential consequences of a fire in occupied settings.