Step 1 — Is there storage?
If storage > 4 m or rack storage is present, you are in storage occupancies. EN: HHS1–HHS4 based on ST1–ST4. NFPA: Chapters 20–25 by commodity class. Skip to storage decision tree.
Step 2 — Is it a process risk?
If processes involve flammable liquids, plastics processing, paint spray, or similar — HHP1–HHP4 (EN) or Extra Hazard Groups 1–2 (NFPA).
Step 3 — Otherwise it's Ordinary or Light
Schools (non-storage), hospitals, libraries = LH (EN) / Light (NFPA). Offices, hotels = OH1 / Light. Shops, restaurants = OH2 / Ordinary 1. Workshops = OH3 / Ordinary 2.
Pitfalls
1) Mezzanines used for storage push an OH room into HHS. 2) A retail floor with pallet displays can shift from OH2 to HHS. 3) Server rooms with cardboard packing waste behave more like HHP than LH.
References
- EN 12845:2015 Annex A–C
- NFPA 13 (2022) Chapters 4 and 20
Cite this page
- APA
- FireTwin AI (2026). Hazard classification decision tree (EN 12845 and NFPA 13). FireTwin AI. https://firetwin.eu/learn/hazard-classification
- IEEE
- FireTwin AI, "Hazard classification decision tree (EN 12845 and NFPA 13)," FireTwin AI, 2026. [Online]. Available: https://firetwin.eu/learn/hazard-classification