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Separation of High Hazard Occupancies Calculator
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Separation of Occupancies Having High Hazards Calculator
Looks up required fire-resistance separation ratings (hours) for areas containing high-hazard contents per NFPA 5000 (2024) and NFPA 400 (2025).
Unit system
Select the unit system for area inputs (ft² vs m²). Separation ratings are reported in hours (no unit conversion needed).
Applies to room area inputs used for the Protection Level 3 footnote check.
Inputs
Standard / Table reference
This calculator uses the separation ratings from NFPA 5000 (2024) Table 34.3.2.3 and NFPA 400 (2025) Table 6.2.1.3 (equivalent in the provided extract).
Based on NFPA 5000 (2024) — Table 34.3.2.3 and NFPA 400 (2025) — Table 6.2.1.3
Scenario
Select whether the high-hazard area is adjacent to a non-high-hazard occupancy (occupancy rows),
or adjacent to another high-hazard area (protection-level matrix).
Select the occupancy classification of the adjacent (non-high-hazard) area. This tool does not classify occupancy; use the applicable standard’s definitions.
Choose Protection Level 1–5 for the high-hazard area per the applicable standard. This calculator does not determine protection level; it only applies the table lookup.
Used to evaluate the Protection Level 3 (*) footnote: for rooms > 150 ft² (14 m²) storing flammable liquids, combustible liquids, or Class III oxidizers, the separation must be at least 2 hours.
Choose “Unknown (assume in-scope)” for a conservative check.
Floor area of the room containing the high-hazard contents. Required only when the PL3 footnote could change the result (e.g., table gives 1 hour and the stored material is in-scope).
Threshold for the footnote is > 150 ft² (≈ 14 m²).
ft²
Only used to evaluate the PL3 (*) minimum 2-hour separation note when applicable.
This scenario uses the protection-level matrix within the referenced table (separation between two high-hazard areas).
If Protection Level 3 is involved and the matrix gives 1 hour, the PL3 (*) footnote can require a minimum of 2 hours for certain materials/room sizes.
High-hazard area A
Choose Protection Level 1–5 for high-hazard area A per the applicable standard.
Used only if Protection Level 3 is selected and the matrix gives 1 hour.
For rooms > 150 ft² (14 m²) storing flammable liquids, combustible liquids, or Class III oxidizers, minimum separation is 2 hours.
Floor area of the high-hazard room in Area A. Only required when evaluating the PL3 footnote in a case where the matrix gives 1 hour.
ft²
High-hazard area B
Choose Protection Level 1–5 for high-hazard area B per the applicable standard.
Used only if Protection Level 3 is selected and the matrix gives 1 hour.
For rooms > 150 ft² (14 m²) storing flammable liquids, combustible liquids, or Class III oxidizers, minimum separation is 2 hours.
Floor area of the high-hazard room in Area B. Only required when evaluating the PL3 footnote in a case where the matrix gives 1 hour.
ft²
Assumptions & Applicability
This calculator performs a table lookup of required fire-resistance separation rating (hours) for areas containing high-hazard contents, based on the referenced standards.
You must correctly determine (a) the adjacent occupancy classification and (b) the applicable Protection Level(s) per the applicable standard. This tool does not classify occupancy or protection level.
“NP” means the arrangement is not permitted by the referenced table; consult the full code context and the authority having jurisdiction for compliant alternatives.
The Protection Level 3 (*) footnote is implemented as a minimum 2-hour separation when the base table requirement is 1 hour and the room is > 150 ft² (≈ 14 m²) storing flammable liquids, combustible liquids, or Class III oxidizers.
This tool does not address details such as continuity of barriers, opening protectives, penetrations, duct dampers, shafts, or other code provisions that can affect compliance.
Where the standard states that these separation requirements are not reduced based on fire protection system installations, this calculator does not apply any sprinkler-based reductions.
References
NFPA 5000 (2024): Separation of occupancies having high hazards — Table 34.3.2.3.
NFPA 400 (2025): Separation of occupancies having high hazards — Table 6.2.1.3.
Protection Level 3 (*) note implemented: rooms > 150 ft² (≈ 14 m²) storing flammable liquids, combustible liquids, or Class III oxidizers require not less than a 2-hour separation (applied when it changes the outcome).
