Codes, Standards, and Regulations
Codes, standards, and the chain of adoption
A code (NFPA 1, NFPA 101, the IBC/IFC family) states broad mandatory requirements and adopts standards (NFPA 13, 72, 25, 20, 70) by reference. The edition in force is the one the authority having jurisdiction adopted - not the newest printed edition - and local amendments override model text. Questions frequently test this hierarchy.
Reading a document correctly
Only the main body is enforceable. Annex material (Annex A and similar explanatory text) is not a requirement, though it is persuasive and often quoted in distractors. "Shall" is mandatory; "should" is advisory. NFPA 101 separates new-construction and existing-building requirements into different occupancy chapters, and existing buildings are generally not required to meet new-construction criteria absent a retrofit trigger: change of use, addition, or a specific retroactive requirement (for example, sprinklers in certain high-rise or health care occupancies). The administrative chapters (1–4) apply throughout. NFPA documents move on scheduled revision cycles with formal letter ballots and Tentative Interim Amendments issued between editions.
Occupancy drives everything
Classification (assembly, business, educational, health care, industrial, mercantile, residential, storage, detention) sets occupant load factors, egress geometry, and required fire protection features. Mixed occupancies may be treated as separated (rated barriers between) or non-separated (the most restrictive requirements govern the whole).
Worked example
A 10,000 ft² business tenant: NFPA 101 applies 100 ft² gross per occupant, giving 100 occupants. At 0.2 in of width per occupant, the calculated egress width is only 20 in - far below the 36 in minimum clear corridor width, and an occupant load above roughly 49 requires two means of egress. The arithmetic rarely governs; minimums and the number-of-exits rules do.
Traps
Citing an edition not adopted; quoting Annex A as a requirement; missing that the occupancy chapter modifies Chapter 7; overlooking the AHJ's equivalency authority.