FM Global DS 8-1: Commodity Classification — Class 1 to 4 and Plastics

The first step in warehouse sprinkler design is commodity classification; the protection tables in DS 8-9 are selected directly from it. This article follows the text of FM Global DS 8-1 "Commodity Classification" (April 2014, Interim Revision October 2025, 23 pages); numbers in brackets are the section, figure and table numbers of the data sheet.

1. What a commodity is and how the class is found (Section 2.1, 2.2)

Under DS 8-1 a commodity is more than the stored product: the material, its internal packaging, the external packaging (e.g. a cardboard carton) and the material-handling aid (e.g. the pallet) are assessed together (2.1, Figure 2.1). The class is determined in three steps (2.2):

1. Material and internal packaging are evaluated with Sections 2.2.1 to 2.2.6; where noncombustibles, ordinary combustibles, unexpanded and expanded plastic are combined, Figure 2.2.7 is used. Only the material and internal packaging count when the percentage of plastic is determined. The density of expanded plastic may be taken as 2 lb/ft³ (32 kg/m³).
2. The effect of external packaging is added per Section 2.2.8.
3. The effect of the pallet is added per Section 2.2.9.

The examples in Table 2.3 are an aid to these steps. The "material" described there may be the stored material alone, the material with its internal packaging, or the material with internal and external packaging; any component the description does not cover is evaluated separately using the three steps.

2. The eight commodity classes (Section 2.2.1 to 2.2.6)

FM standard commodities are ranked from lowest to highest hazard as follows: noncombustible → Class 1 → Class 2 → Class 3 → Class 4/cartoned unexpanded plastic (CUP) → cartoned expanded plastic (CEP) → uncartoned unexpanded plastic (UUP) → uncartoned expanded plastic (UEP).

• Noncombustible (2.2.1): materials that do not burn. Noncombustible commodities do not require sprinkler protection by themselves; however, sprinklers are required where there are combustibles in the construction, the occupancy or material-handling processes. Even where occupancy and construction are currently noncombustible, sprinklers should be considered to accommodate future changes to storage, occupancy or construction.
• Class 1 (2.2.2): noncombustible materials on wood or FM Approved pallets; or noncombustible materials in single-layer corrugated cardboard cartons (with or without single-thickness dividers) or ordinary paper wrappings, on wood or FM Approved pallets. A negligible amount of plastic trim such as knobs or handles is acceptable.
• Class 2 (2.2.3): noncombustible or Class 1 commodities in multiple-thickness corrugated cardboard cartons, slatted wooden containers, solid wooden boxes or equivalent combustible packaging, on wood or FM Approved pallets.
• Class 3 (2.2.4): cellulosic materials such as wood, paper or natural textiles (cartoned or not, on wood or FM Approved pallets); and Class 1, 2 and 3 materials containing no more than 5% plastic (unexpanded, expanded or both) by either weight or volume.
• Class 4/unexpanded plastic, UP (2.2.5): for a single pallet load, (A) the total weight or volume of unexpanded plastic is more than 5%, (B) the total volume of expanded (foam) plastic is from 5% to 40%, or (C) the expanded plastic is exposed or on the outer portion of the material (protecting or enveloping it) and its volume is more than 5% and up to 20% (Figure 2.2.5.1). In corrugated cartons it is treated as cartoned unexpanded plastic (CUP)/Class 4; otherwise as uncartoned unexpanded plastic (UUP). Exceptions are listed in Table 2.3.
• Expanded plastic, EP (2.2.6): (A) the total volume of expanded plastic is more than 40%, (B) the expanded plastic is exposed or envelops the material and its volume is more than 20%, or (C) empty plastic containers larger than 32 oz (1 L) that are not nested. In cartons it is CEP, otherwise UEP. Exceptions are listed in Table 2.3.

According to the revision history, the April 2014 edition removed the Group A, B and C plastics categories, so plastics are now classified only as unexpanded or expanded; Class 4 was also removed as a separate class and is treated and protected as cartoned unexpanded plastic (CUP) (Appendix B).

3. Decision flow by plastic content (Figure 2.2.7)

Figure 2.2.7 asks the following questions, in order, for cartoned commodities whose material and internal packaging contain plastic:

1. Does the material and internal packaging contain more than 5% plastic (unexpanded, expanded or both) by weight or volume? If not, Class 1, 2 or 3.
2. If so, does it contain more than 40% expanded plastic by volume? If yes, expanded plastic.
3. If not, does it contain more than 20% expanded plastic by volume? If not, unexpanded plastic.
4. If so, is that more than 20% of expanded plastic exposed or on the outer portion of the material (Figure 2.2.5.1)? If yes, expanded plastic; if not, unexpanded plastic.

If the material is in a corrugated carton the result is named accordingly: unexpanded plastic in cartons becomes CUP, expanded plastic in cartons becomes CEP. If the material is stored in plastic containers, the material and internal packaging are classified first with Figure 2.2.7 and the plastic container is then evaluated with Section 2.2.8 and Table 2.3 (2.2.7).

4. The effect of external packaging (Section 2.2.8)

External packaging governs the early stages of fire growth; if it is a higher or lower hazard than the material inside, the classification is raised or lowered accordingly.

• Corrugated cardboard cartons (2.2.8.1): they absorb sprinkler water, wetting the commodity and reducing fire spread; on the other hand they burn easily, carry fire quickly up the storage array and operate sprinklers sooner. Without cardboard, a fire can grow low in the array and be larger when the first sprinkler operates. Plastics in corrugated cartons are treated as cartoned plastics (CUP or CEP); noncombustible solids in corrugated cartons are protected as Class 1.
• Partial packaging (2.2.8.1.1): a carton counts as fully cartoned if only one side has been removed, or if more than one side has been removed but cardboard still covers at least the bottom, the top and 75% of the total area of the four vertical sides. If the top is completely removed and sprinkler water can be collected, the open-top container guidance of DS 8-9 applies.
• Solid metal containers (2.2.8.2): they decrease the hazard. Plastics in a five-sided, open-top solid metal container are treated as Class 3; plastics in a solid metal container with a solid metal top are treated as Class 1.
• Plastic containers (2.2.8.3): in general the plastic container drives the fire protection; the class is read from Table 2.2.8.3 below.
• Wood crates (2.2.8.4): solid wooden crates at least 0.25 in. (6.3 mm) thick decrease the hazard; plastics in a five-sided, closed-top solid wooden crate are treated as Class 3, except when the commodity is lithium-ion batteries.
• Encapsulation (2.2.8.5): it does not significantly change the classification, but it limits pre-wetting and must be accounted for in the sprinkler design. The protection guidelines of DS 8-9 already account for encapsulation.
• Flexible intermediate bulk containers, supersacks (2.2.8.6): once the bag burns through, the free-flowing contents spill out and fire intensity falls. Combustible supersacks of inert free-flowing material are protected as Class 1; combustible supersacks of free-flowing unexpanded plastic are protected as CUP.

A "solid" container has no openings in its sides or bottom; a "gridded" container is significantly open on the sides and/or bottom (Figures 2.2.8.3-1 and 2.2.8.3-2).

5. The effect of pallets (Section 2.2.9)

• Wood or FM Approved pallets (2.2.9.1): no increase in classification; only where noncombustible materials are stored on them is the commodity treated as Class 1. Cardboard pallets are treated as wood pallets for classification (2.2.9.1.1); cardboard pallets are not used for ignitable liquid handling (2.2.9.1.2); FM Approved pallets are used with ignitable liquid storage only where DS 7-29 allows (2.2.9.1.3).
• Unexpanded plastic pallets, not FM Approved (2.2.9.2): no increase if the material is already a plastic (CUP, CEP, UUP or UEP). Otherwise the class rises by one level: Class 1 → Class 2, Class 2 → Class 3, Class 3 → CUP.
• Expanded plastic pallets, not FM Approved (2.2.9.3): no increase if the material is already an expanded plastic. Otherwise the pallet volume is taken into account; in the data sheet's own example, a pallet making up 15% by volume of the overall pallet load makes the commodity expanded plastic.
• Default assumptions where data are missing (2.2.9.4): expanded plastic density 2 lb/ft³ (32 kg/m³); high-density polyethylene plastic pallet 55 lb (25 kg); hardwood pallet 38 lb (17 kg); pallet dimensions 40 × 48 × 6 in. (1 m × 1.2 m × 152 mm); solid-piled commodity volume on a pallet 60 ft³ (1.7 m³).

Storage of idle pallets is outside DS 8-1 and is covered by DS 8-24 (Section 1.1).

6. Examples from Table 2.3 (Section 2.3)

The classes in Table 2.3 are examples only and are based on what is described as the "material"; they do not necessarily account for packaging, storage configuration or pallets, and products vary between manufacturers. A material listed as UP or EP becomes CUP or CEP when cartoned and UUP or UEP when uncartoned; metal parts listed as noncombustible become Class 1 in single-layer corrugated cartons (2.3). The rows below are taken from the table; the first column is the item number in Table 2.3.

Special commodities are outside the scope of DS 8-1 and are protected to their own data sheets (Section 1.1): rubber tires (DS 8-3), baled fiber (DS 8-22; its April 2026 revision, Baled Storage, incorporated DS 8-7 Baled Fiber Storage and made it obsolete), hanging garments (DS 8-18), roll paper (DS 8-21), baled waste paper (DS 8-22), rolled nonwoven fabrics (DS 8-23), pallets (DS 8-24) and carpets (DS 8-30). Special hazards such as ignitable liquids (DS 7-29), aerosols (DS 7-31) and compressed gases (DS 7-50), and carousel (DS 8-33) and automatic storage and retrieval (DS 8-34) systems containing high-value equipment, also go to their own data sheets. Protection of empty plastic intermediate bulk containers (IBCs), by contrast, is given in DS 8-1 itself, in Section 2.4.2 and Table 2.4.2.1.

7. Mixed storage and configuration (Section 2.4.1, 3.2)

Stored commodities are classified with DS 8-1 and protected with DS 8-9, and protection is based on the highest-hazard commodity at the facility (2.4.1.1). The alternative to protecting the whole facility for the highest hazard is to segregate that commodity from the rest of the facility and protect it accordingly (2.4.1.2); the data sheet notes that keeping the highest-hazard commodity properly segregated can be very difficult in normal warehouse operations. DS 8-1 does not give an aisle width or distance for this segregation.

Section 3.2.1 gives the reasons for protecting for the highest hazard rather than for an average of the commodities:

• In fire tests, replacing one tier of a four-tier rack array with a higher-hazard commodity produced a hazard much higher than a rack filled entirely with the lower-hazard commodity.
• In tests where sprinkler protection is adequate for the commodity, typically 200-300 ft² (19-28 m²) of commodity burns, and this small amount creates a relatively large sprinkler operating area of 1,500-2,500 ft² (140-230 m²). Introducing a more hazardous commodity may enlarge the burning area and overtax a system designed for the lower hazard.
• "Averaging the commodities" requires continual monitoring to ensure that concentrations of higher-hazard commodities are not exceeded; in normal warehouses adequate monitoring is very difficult and generally not feasible.

Classification depends on configuration as well as material (3.2.2): a solid block of wood is hard to ignite and slow to burn, but in a configuration with a large surface area and parallel surfaces (e.g. idle wood pallets) it burns much more rapidly. For mixed materials, the proportions of different combustibles are considered together with packaging and configuration; if a higher- or lower-hazard material envelops the others, the classification is adjusted accordingly.

8. Why plastics are worse, and how the class is found by testing (Section 3.1)

The heat of combustion of ordinary combustibles is generally 6,000-8,000 Btu/lb (13,960-18,600 kJ/kg), and that of plastics 12,000-20,000 Btu/lb (27,910-46,520 kJ/kg); the maximum burning rate of plastics is often two to three times that of similarly arranged ordinary combustibles (3.1.1.1). A plastic with a high proportion of inert filler may show a measured heat of combustion in the ordinary combustible range, yet in the data sheet's intermediate-scale test a commodity of 52% inert and 48% polyester/polystyrene created a hazard well above that of ordinary combustibles (3.1.1.2).

Bench-scale tests such as the oxygen bomb calorimeter and the fire propagation apparatus (FPA) are an inexpensive way to prove high combustibility but are usually not appropriate for proving low combustibility, and their results must be evaluated very conservatively (3.1.2). A conclusive result comes from commodity classification tests under the fire products collector (FPC), on a double-row rack segment, compared against the FM standard commodities of Table 3.1.3 (3.1.3): metal-lined double tri-wall cartons for Class 2; paper cups in compartmented cartons for Class 3; unexpanded polystyrene cups in compartmented cartons for CUP; expanded polystyrene foam plates in corrugated cartons for CEP; plastic pallets for UUP; and exposed foam plates for UEP. All are stored on wood pallets, and most of the protection guidelines in DS 8-9 are based on large-scale fire tests using these standard commodities.

9. The link into DS 8-9

DS 8-9 requires the commodity hazard in a storage area to be determined with DS 8-1 and protection to be based on the most severe commodity hazard present anywhere in that area (DS 8-9 2.2.2.1, 2.2.2.2). The ceiling-level protection tables are split by class as follows:

• Rack storage is protected either by ceiling-only sprinklers or by ceiling-level and in-rack sprinklers together; whether in-rack sprinklers are needed depends on commodity hazard, ceiling height, available water supply, solid shelves or open-top containers and flue spaces, and is determined with DS 8-9 Figure 3 (DS 8-9 2.3.4.1, 2.3.4.2).
• The combustibility of pallets is included in the overall commodity classification; idle pallets are protected to DS 8-24 (DS 8-9 2.2.5.2, 2.2.5.3).
• Where the most severe commodity exists in relatively small amounts throughout the area and protecting it is a challenge, DS 8-9 Scheme 8-9A applies (DS 8-9 2.2.2.3).

For reading the tables and the in-rack decision, see the DS 8-9 article.

Quick checklist

• All commodities listed; material, internal packaging, external packaging and pallet identified separately
• Plastic percentage calculated from the material and internal packaging only, by weight and by volume; the 5%, 20% and 40% thresholds applied with Figure 2.2.7
• External packaging (cartons, metal containers, plastic containers, wood crates, supersacks) assessed with Section 2.2.8 and Table 2.2.8.3
• Pallet type checked; one-level increase applied for non-FM Approved plastic pallets
• Where a Table 2.3 example does not cover packaging and pallet, completed with the three steps
• Protection based on the highest-hazard commodity at the facility, or that commodity segregated and protected on its own
• Special commodities (tires, roll paper, pallets, lithium-ion batteries etc.) referred to their own data sheets
• Classification carried into the correct DS 8-9 protection table

Frequently Asked Questions

What class is a plastic product in a cardboard carton?

Under Figure 2.2.7 only the material and internal packaging are considered. If plastic does not exceed 5% by weight and by volume, the commodity is Class 1, 2 or 3. Above 5% it is unexpanded plastic, and in a corrugated carton it becomes cartoned unexpanded plastic (CUP), i.e. Class 4. If expanded plastic exceeds 40% by volume, or exceeds 20% and is exposed on the outside of the material, the commodity is expanded plastic and, cartoned, is treated as cartoned expanded plastic (CEP).

Are Class 4 and Group A plastics still separate classes in DS 8-1?

No. The April 2014 edition removed the Group A, B and C plastics categories; plastics are classified only as unexpanded or expanded. Class 4 was also removed as a separate class and is treated as cartoned unexpanded plastic (CUP) (DS 8-1 Appendix B, Section 2.2.5). That is why DS 8-9 Tables 3 and 8 cover Class 4 and cartoned unexpanded plastic together.

Are idle pallets classified with DS 8-1?

No. DS 8-1 Section 1.1 refers pallet storage to DS 8-24, and DS 8-9 requires idle pallets to be protected to DS 8-24 (DS 8-9 2.2.5.3). In DS 8-1 Table 2.3, idle plastic pallets that are not FM Approved (item 150) are listed as uncartoned unexpanded plastic (UUP) with a reference to DS 8-24. Section 3.2.2 notes that idle wood pallets, with their large surface area and parallel surfaces, burn much more rapidly than solid wood.

How does a plastic pallet affect the commodity class?

Wood, cardboard and FM Approved pallets do not increase the class (2.2.9.1). A non-FM Approved unexpanded plastic pallet raises the class by one level when the material is not already a plastic: Class 1 → Class 2, Class 2 → Class 3, Class 3 → CUP (2.2.9.2). With a non-FM Approved expanded plastic pallet, if the material is not expanded plastic the pallet volume is taken into account; in the data sheet's example, a pallet making up 15% by volume of the overall pallet load makes the commodity expanded plastic (2.2.9.3).

Which commodity governs protection in mixed storage?

The highest-hazard commodity at the facility (DS 8-1 2.4.1.1; DS 8-9 2.2.2.2). Commodities are not averaged: under Section 3.2.1, replacing even one tier of a four-tier rack with a higher-hazard commodity greatly increases the hazard, and continual monitoring of an average is not feasible in normal warehouses. The alternative is to segregate the highest-hazard commodity and protect it accordingly (2.4.1.2); DS 8-1 gives no aisle width for this and notes that keeping it segregated can be very difficult in normal operations.

Which DS 8-1 class do lithium-ion batteries fall into?

DS 8-1 does not assign a class to lithium-ion batteries. Item 7 of Table 2.3 refers lithium-ion cells, modules and products with lithium-ion batteries to DS 7-112; the lithium-ion guidance was relocated from DS 8-1 to DS 7-112 in the October 2024 interim revision (Appendix B). The wood crate reduction of 2.2.8.4 also does not apply when the commodity is lithium-ion batteries. Dry cell batteries other than lithium metal and lithium-ion are Class 1 uncartoned and Class 2 cartoned (items 1 and 3).

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