The Smoke Developed Index is derived from measurements of smoke obscuration versus time for a material tested in accordance with NFPA 255.

• A. Life Safety Evaluation
• B. Smoke Developed Index
• C. Flame Spread Index
• D. Occupant Load

Answer: (B)

The main idea here is what the Smoke Developed Index represents. This index quantifies how much smoke a material emits as it burns, based on measurements of smoke obscuration (how opaque the smoke is) over time in a standardized test setup. In NFPA 255, a sample is subjected to controlled heat, and the resulting smoke production is tracked as the fire develops. The SDI is calculated from that obscuration–time data, giving a single value that indicates the material’s smoke-producing potential. This is distinct from the Flame Spread Index, which relates to how quickly flames travel across a surface, and from occupancy-related metrics like Life Safety Evaluation or Occupant Load. So, the statement that the Smoke Developed Index comes from smoke obscuration versus time in NFPA 255 is correct.