The same pallet carries three different names in three standards. NFPA calls it Class III, EN 12845 calls it Category III, FM Global calls it Class 3 — and they are not the same thing. This page maps the three systems, and shows where the mapping breaks.
Three systems, three logics
- NFPA 13 (2025): the product is classified as Class I to IV, and plastics are classified separately as Group A/B/C, expanded or nonexpanded (20.4). A Class III product may contain up to 5 percent by weight of nonexpanded or 5 percent by volume of expanded Group A/B plastic (20.4.3.2); more than that moves it to Class IV (20.4.4) and, beyond set limits, to a Group A plastic commodity (20.4.5.3–20.4.5.4).
- EN 12845: the material factor (M1 to M4) is determined first; the physical form of the goods (exposed plastic surface, open structure, solid block, granules and so on) converts it to Category I to IV through Table B.1. If the product is also listed in Table C.1, the higher category applies (B.3.1). The storage configuration (ST1 to ST6) is a separate input used in the density and height tables.
- FM Global (DS 8-1): DS 8-9 (2.2.2.2) ranks commodity hazards from lowest to highest as Class 1, 2, 3, 4 and the plastic categories: unexpanded plastic (cartoned CUP and uncartoned UUP) and expanded plastic (CEP, UEP) (2.2.2–2.2.6).
Approximate mapping table
| Commodity description | NFPA 13 | EN 12845 | FM Global |
|---|---|---|---|
| Non-combustible product in cartons on timber pallets (metal parts, canned goods) | Class I (20.4.1) | Category I (M1) | Class 1 (2.2.2) |
| Non-combustible product in timber crates or multi-layer cartons | Class II (20.4.2) | Category I–II | Class 2 (2.2.3) |
| Timber, paper, natural fibre; plastic 5 percent or less | Class III (20.4.3) | Category I–II (M1; Table C.1 mostly gives II for paper and timber) | Class 3 (2.2.4) |
| Cartoned, containing 5–15 percent by weight nonexpanded or 5–25 percent by volume expanded Group A plastic | Class IV (20.4.4.1) | Category II (M2 with no special configuration; Figure B.1 and Table B.1) | Class 4/CUP (plastic above 5 percent; 2.2.5) |
| Cartoned nonexpanded plastic | Cartoned nonexpanded Group A | Category III (M3) | CUP |
| Exposed nonexpanded plastic | Exposed nonexpanded Group A | Category III (exposed unexpanded plastic surface; Table B.1) | UUP |
| Exposed expanded plastic (foam, EPS) | Exposed expanded Group A | Category IV (M4; B.3.4) | UEP |
| PE/PP storage bins (empty or full) | Group A plastic (20.4.5.1) | Category IV regardless of contents (G.8.2) | Per the plastic container table (Table 2.2.8.3) |
| Idle pallets | Idle pallet rules (20.17) | Annex G.5 (Tables G.5–G.6) | DS 8-24 |
| Tyres | Separate rubber tire criteria | Horizontal storage Category IV (Table C.1); rubber treated as plastic (B.2.1) | Separate data sheet (DS 8-3) |
Where does the mapping break?
First break: counting the pallet. EN 12845 treats the stored goods as product plus packaging plus pallet, and includes the pallet in the plastic content (B.2.1). NFPA 13 (20.3.2) and FM DS 8-1 (2.2.9) assume wood pallets and raise the class for plastic pallets. A calculation made on the assumption of timber pallets can fall short in all three standards once the site moves to plastic pallets.
Second break: orientation. In EN 12845, storage orientation changes the category for rolled goods; per Table C.1, corrugated cardboard rolls stored horizontally are Category III and stored vertically Category IV. NFPA does not draw that distinction as sharply.
Third break: above 5 percent. All three standards use 5 percent as the lower threshold: EN 12845 for M1 (5 percent by mass nonexpanded and 5 percent by volume expanded, B.2.2), NFPA for Class III (the same 5 percent limits, 20.4.3.2) and FM for Class 3 (5 percent by weight or volume, 2.2.4). They diverge above it: for cartoned goods NFPA calls it Class IV up to 15 percent by mass or 25 percent by volume, FM treats anything above 5 percent directly as plastic (UP), and EN splits M2 to M4 through Figure B.1; for expanded plastic, FM and EN use a 40 percent by volume threshold (2.2.6.1; B.2.5). The same product can land in two different classes under two standards.
Rule: the mapping is only a first orientation. Once the class is set, the calculation is redone with the chosen standard's own table. Using a density-area value read from the mapping table directly is wrong.
Storage configuration: EN 12845's second axis
In EN 12845 the category alone is not enough; the storage configuration (ST1 to ST6; 6.3.2) drives the design. Free-standing or block stacking (ST1) and palletised racking (ST4) give different results for the same commodity: the vertical flues of a rack drive rapid vertical flame spread, whereas in block stacking the fire spreads over the surface. That is why a Category I product at 7.5 mm/min reaches 5.3 m in ST1 but only 4.7 m in ST4 (Table 4).
Practical workflow
- Define the product as a whole, including packaging and pallet.
- Measure the plastic content by mass and by volume (the 5 percent thresholds and above).
- Enter the chosen standard's own classification table.
- Add the storage configuration and the storage height.
- Read the density-area or sprinkler-pressure combination from that standard.
- Put a commodity classification schedule in the handover file: product, packaging, pallet, class, justification, selected density.
That last step is the single page that most reduces the number of returns during insurance and inspection review.
Frequently Asked Questions
Are NFPA Class IV and EN 12845 Category IV the same?
No. NFPA Class IV is a cartoned product containing more than 5 and up to 15 percent by weight of nonexpanded, or more than 5 and up to 25 percent by volume of expanded, Group A plastic, or one made of Group B plastics (NFPA 13 20.4.4.1). EN 12845 Category IV is the highest category: expanded plastics (M4), exposed expanded plastic surfaces and PE/PP bins fall into it (Annex B, G.8.2). The numbering is similar but the content differs; a project-specific check is essential.
Is the pallet part of the classification?
In EN 12845 yes: packaging and pallet are included when the plastic content is assessed (B.2.1). NFPA 13 (20.3.2) and FM DS 8-1 (2.2.9) assume wood pallets and raise the commodity class where unlisted or non-approved plastic pallets are used. A calculation based on wood pallets can fall short in all three standards once the site moves to plastic pallets.
Which class do PE/PP plastic bins fall into?
Category IV in EN 12845 regardless of their contents (G.8.2). In palletised racking (ST4) in-rack sprinklers are required at no more than 1.5 m horizontally and 2 m vertically; in all other storage the height is limited to 3 m, and a film-forming foam additive is added to the sprinkler water (G.8.3–G.8.5).
Can I use the density from the mapping table directly?
No. The mapping is only a first orientation. Once the class is set, the calculation must be redone with the chosen standard's own table.
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Download MEP Calc on the App StoreFM Global Property Loss Prevention Data Sheets 8-1 and 8-9. NFPA 13 (2025) storage chapters and commodity classification. EN 12845:2015+A2:2026 material factor and commodity category annexes. The mapping is approximate; design always follows the tables of the chosen standard.