FM Global, NFPA and EN 12845 Storage Class Mapping

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: two axes. The product itself (Class I to IV) and its plastic content (Group A/B/C, expanded or unexpanded) are classified separately.
• EN 12845: one axis. The material factor (M1 to M4) multiplied by the storage configuration gives a single Category (I to IV).
• FM Global: Class 1 to 4 plus plastic groups; but the design curve ties directly to stack height and protection type.

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	Category I	Class 1
Non-combustible product in timber crates, limited combustible packaging	Class II	Category I–II	Class 2
Timber, paper, natural fibre; no plastic	Class III	Category II–III	Class 3
Containing a limited quantity of Group A plastic	Class IV	Category III	Class 4
Cartoned unexpanded plastic	Cartoned Unexpanded Group A	Category III–IV	Cartoned Unexpanded
Exposed unexpanded plastic	Exposed Unexpanded Group A	Category IV	Uncartoned Unexpanded
Exposed expanded plastic (foam, EPS)	Exposed Expanded Group A	Category IV (M4)	Uncartoned Expanded
PE/PP storage crates (empty or full)	Group A plastic	Category IV, unconditionally	Uncartoned plastic
Empty timber pallets	Idle pallet rules	Separate annex rules	DS 8-24
Rubber goods	Group A equivalent, separate curve	Treated as plastic (M3)	Separate DS

Where the mapping breaks

First break: counting the pallet. EN 12845 treats stored goods as product plus packaging plus pallet as one whole. A calculation done assuming timber pallets falls short once the site moves to plastic. NFPA handles the pallet as a separate subject.

Second break: orientation. In EN 12845, storage orientation changes the category for rolled products: a horizontal corrugated roll is Category III and a vertical roll Category IV. NFPA does not draw that distinction as sharply.

Third break: the 5 percent threshold. EN 12845 uses thresholds of 5 percent unexpanded plastic by mass and 5 percent expanded by volume. The NFPA Group A definition is built on different logic. The same product can fall into two different classes in the two standards.

Storage configuration: EN 12845's second axis

In EN 12845 the material factor alone is not enough; it combines with the storage configuration (ST1 to ST6). Free-standing block stacking (ST1) and pallet racking (ST4) give different results for the same commodity: the vertical channels of racking produce a flag fire, while a block stack spreads from the surface. So for a Category I product, 7.5 mm/min is sufficient up to 5.3 m in ST1 but only to 4.7 m in ST4.

Practical workflow

1. Define the product as a whole, including packaging and pallet.
2. Measure the plastic content by mass and by volume (the 5 percent thresholds).
3. Enter the classification table of the chosen standard.
4. Add the storage configuration and the stack height.
5. Read the density-area or sprinkler-pressure combination from that standard.
6. 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 review iterations with insurers and inspectors.

Frequently Asked Questions

Are NFPA Class IV and EN 12845 Category IV the same?

The numbering is similar but the content differs. NFPA classifies product and plastic content on two separate axes; the EN Category is the resultant of material factor and storage configuration. They map roughly, but must be checked project by project.

Is the pallet part of the classification?

In EN 12845 yes: stored goods are assessed as product, packaging and pallet together. A calculation assuming timber pallets falls short once plastic pallets are used.

Which class do PE and PP crates fall into?

Category IV under EN 12845, regardless of contents. ESFR or in-rack protection is usually mandatory.

Can I use the density from the mapping table directly?

No. The mapping is only for initial orientation. Once the class is set, the calculation must be redone with the tables of the chosen standard.

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