Occupancy Hazard Classification Number : A series of numbers from 3 through 7 that are mathematical factors used in a formula to determine total water supply requirements
NFPA 1142 Standard on Water Supplies for Suburban and Rural Fire Fighting, 2001 ed. https://www.nfpa.org/assets/files/AboutTheCodes/11 42/1142-A2001-ROP.PDF, (Std: Wtr Supp for Suburban and Rural Fr Fight - Amer) {383 NFC}