In NFPA 13, how are hazard classifications mapped to design densities?

• A. Light hazard uses lower density per area, ordinary hazard uses moderate density, and extra hazard uses the highest density
• B. Light hazard uses the highest density; ordinary hazard uses the lowest density; extra hazard uses the middle density
• C. Density is the same for all hazards
• D. They are not related

Answer: (A)

In NFPA 13, the design density is chosen to match how much fire energy is expected in a space. Areas with low fire load are given the smallest design density, areas with a moderate fire load get a middle density, and areas with the highest fire risk get the highest density. This ensures the sprinkler system delivers enough water per square foot to control or suppress a fire relative to how severe it could be. The result is that light hazard receives the lowest density, ordinary hazard a moderate density, and extra hazard the highest density.