Why the category comes first
In EN 12845+A2 the fire hazard of stored goods depends on the combustibility of the product and its packaging and on the storage configuration (6.3.1). The design criteria follow from the storage category (I–IV), the storage configuration (ST1–ST6) and the storage height read together. The Figure 2 flow chart gives three routes: special hazards use the criteria of Annex G, goods containing plastic or rubber use the Annex B method, all others the Annex C alphabetical list.
Annex C: from product name to category
Table C.1 applies where any packaging, with or without pallets, is no more hazardous than a cardboard box or a single layer of corrugated cardboard wrapping. One product can sit on several rows: lightweight paper (below 5 kg/100 m²) in horizontal rolls is Category III and in vertical rolls Category IV; corrugated board rolls are III horizontal and IV vertical; sawn timber is III in ventilated stacks and II otherwise. Some comments add conditions: carpets without plastic and electrical cable require in-rack sprinklers when stored in racks; baled cotton, flax, hemp, waste paper and vegetable fibres might need special measures such as an increased area of operation.
Annex B: material factor and Table B.1
The goods include the product, all packaging and the pallet, and rubber counts as plastic (B.2.1). The material factor is read from Figure B.1:
| Factor | Definition (Figure B.1) | Clause |
|---|---|---|
| M1 | less than 5 % by mass unexpanded and less than 5 % by volume expanded plastic | B.2.2 |
| M2 | more plastic than M1; expanded up to 25 % by volume, unexpanded up to 15 % by mass (below the sloping boundary) | B.2.3 |
| M3 | predominantly unexpanded plastic, or 25–40 % by volume expanded plastic | B.2.4 |
| M4 | more than 40 % by volume expanded plastic | B.2.5 |
The factor is converted into a category by the form of the goods in Table B.1 (B.3.1):
| Configuration | M1 | M2 | M3 | M4 |
|---|---|---|---|---|
| Exposed plastic container with non-combustible contents | I / II / III | IV | ||
| Exposed plastic surface — unexpanded | III | III | III | IV |
| Exposed plastic surface — expanded | IV | IV | IV | IV |
| Open structure | II | II | III | IV |
| Solid block materials | I | I | II | IV |
| Granular or powdered material | I | II | II | IV |
| No special configuration | I | II | III | IV |
Plastic containers with non-combustible liquids are Category I, small (≤ 50 l) containers with non-combustible solids II and larger ones III (B.3.2). The granular/powder row does not apply to rack storage (B.3.7 NOTE 2). Where Table C.1 also gives a category, the higher of the two is used (B.3.1); in the tool this comparison happens automatically when “more hazardous packaging” is chosen on the Annex C route.
Storage within OH or HHS?
Goods may be stored in an area classified as OH provided the protection throughout the room is at least OH3, the storage does not exceed Table 1, a single block does not exceed 50 m² and at least 2.4 m clearance is kept around it (6.2.3). If the area is OH4, or these conditions cannot be met, the storage is HHS.
| Table 1 — max storage for OH3 | ST1 | ST2–ST6 |
|---|---|---|
| Category I | 4.0 m | 3.5 m |
| Category II | 3.0 m | 2.6 m |
| Category III | 2.1 m | 1.7 m |
| Category IV | 1.2 m | 1.2 m |
ST6 stays within this table only as gondola shelving of 1.2 m total width with a solid central barrier from base to top; all other ST6 storage is HHS (Table 1 note b).
HHS: Table 4 and in-rack sprinklers
Table 4 gives, for roof or ceiling protection only, the maximum storage height by category and storage configuration together with the design density (7.5–30.0 mm/min) and the area of operation (260 or 300 m²). These heights are the maximum for ceiling-only protection; above them intermediate in-rack sprinklers are required per 7.2.3 (7.2.2.2). For example, on ST4 palletized racks Category III goods can be protected from the ceiling up to 6.0 m (30.0 mm/min over 300 m²); for Category I the limit is 6.8 m (12.5 mm/min over 260 m²). With in-rack sprinklers the ceiling needs at least 7.5 mm/min over 260 m²; if goods are stored above the top in-rack level, the ceiling criteria come from Table 5 (7.2.3.2).
Where the clearance between the top of storage and the ceiling sprinklers exceeds 4 m, either the density is increased (+2.5 mm/min for the first excess metre, +1 mm/min for each further metre, at least K115) or in-rack sprinklers are installed (7.2.2.3). For ST4 and ST5, protection without in-rack sprinklers is limited to ceiling sprinklers less than 4 m above the goods (Table 2 note c). Dry and alternate systems need a 25 % larger area of operation (Table 4 note); for buildings above 12 m the authorities shall be consulted (7.2.2.1).
Annex G: special hazards
Aerosols (G.2), multiple-tier hanging garments (G.3), flammable liquids (G.4), idle pallets (G.5, G.6), spirit based liquors in wooden barrels (G.6), non-woven synthetic fabric (G.7) and polypropylene/polyethylene storage bins (G.8) have their own Annex G criteria. PP/PE storage bins are classified as HHS Category IV, with a film-forming foam added to the sprinkler water (G.8.2, G.8.5).
Frequently Asked Questions
Should I use Annex C or Annex B of EN 12845?
Per Figure 2, goods containing plastic or rubber go through Annex B, all others through the Annex C alphabetical list; special hazards are in Annex G. Table C.1 applies only where packaging is no more hazardous than a cardboard box or a single layer of corrugated board. If both give a category, the higher one is used (B.3.1).
What is the plastic limit for material factor 1?
Less than 5 % by mass of unexpanded plastic (including the pallet) and less than 5 % by volume of expanded plastic (B.2.2). Exactly 5 % is no longer M1. More than 40 % by volume of expanded plastic is M4 (B.2.5).
How high can goods be stored within an OH area?
Per Table 1, ST1: Category I 4.0 m, II 3.0 m, III 2.1 m, IV 1.2 m; ST2–ST6: 3.5 / 2.6 / 1.7 / 1.2 m. The room must be protected to at least OH3, a single block must not exceed 50 m² and 2.4 m clearance is required around it (6.2.3). Above these limits the storage is HHS.
When are in-rack sprinklers required?
When storage exceeds the ceiling-only height in Table 4 for the category and configuration (7.2.2.2); for ST4 and ST5 when the ceiling sprinklers are more than 4 m above the goods (Table 2 note c); for ST6 in HH, Table 2 only lists in-rack protection. Carpets without plastic and electrical cable stored in racks also need them (Table C.1).
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