Framework / Assessment California Forests and Rangelands: Proposed Indicators Summary Provides a measure of risk for existing Intermix areas, based on the associated Fire Hazard Severity Zone (FHSZ) class. Intermix is defined as between 1 house/2 acres, and 1 house/20 acres (0.5 to 0.05 houses/acre). Landscapes with housing densities of less than 1 house per 2 acres typically retain most of their natural vegetation fuels, and consequently are not as resilient to wildfires as denser urbanized areas. Although wildfires are more frequent in these types of environments, infrastructure values (due to low housing density) are typically relatively low (as compared to urban areas).