Plastic pallets and fire safety: what FM, UL, NFPA and VdS require

Updated on 19 October 2026 · ROLL technical team

In briefWeight for weight, a plastic pallet releases about twice as much energy as wood when it burns, which is why FM, NFPA 13 and VdS rules call for more fire protection. The exception is models that pass a full-scale test such as FM 4996 or UL 2335: they can generally be treated like wood.

Why plastic is treated differently from wood

For fire safety, a plastic pallet weighs more heavily than a wooden one because of the energy it releases when it burns. Wood releases 17-22 MJ per kilo, polypropylene 40-46 MJ/kg ^[5]. For polyethylene, one technical source gives 43.1-43.4 MJ/kg ^[6]. Weight for weight, plastic brings about twice the fire load into the store.

Diagram of the heat of combustion of wood and plastic, with the fire load of three pallets compared — Per kilo, plastic releases about twice as much energy as wood: 40-46 MJ/kg against 17-22.

Per pallet, the sum depends on the weight. A 1200×800 wooden pallet normally weighs about 10-20 kg, so 170-440 MJ. A 16 kg medium-duty plastic pallet, within the 14-20 kg range found in catalogues ^[7], reaches 640-740 MJ with polypropylene values, more than any wooden pallet in that range. A 6 kg lightweight pallet stops at 240-280 MJ, within the range for wood.

Then there is the way it burns. An article in the ICC's technical journal notes that plastic pallets can burn as hot as wood and for longer ^[2]. That is why the rules are stricter.

The fire tests that count: FM 4996 and UL 2335

A plastic pallet can only be treated like wood if it passes a full-scale fire test ^[2].

Test	What is burned	Criterion
FM 4996	8 stacks of pallets about 1.2 m high, lit with 4 petrol-soaked igniters	fire controlled with 5.9 mm/min of water (0.15 gpm/ft²) within 10 minutes
UL 2335, idle pallets	6 stacks about 4 m high under a sprinklered ceiling	number of sprinklers operated, stack stability, fire spread, temperature of a steel beam
UL 2335, loaded pallets	pallets with Class II commodity in a calorimeter	heat released

Source for all three rows: ^[2].

Diagram of the FM 4996 test with eight stacks of plastic pallets under sprinklers — FM 4996: 8 stacks of about 1.2 m, and the fire must be controlled with 5.9 mm/min of water within 10 minutes.

A pallet that passes FM 4996 becomes FM Approved. The approval covers the model tested: ask for the certificate with the exact code of the pallet you are buying.

FM Data Sheet 8-24: inside and outside the building

FM's data sheet on idle pallets is DS 8-24. The edition we read is dated January 2013, revised January 2015 ^[1]: before using it in a project, check on the FM website whether a newer one exists. The values below are given for information only: they do not replace the original data sheet or the fire protection design.

Indoors, a plastic pallet that is not FM Approved is classed as unexpanded plastic, uncartoned (UUP) and protected according to DS 8-9. The rule applies to 2-way and 4-way, closed-deck and composite pallets. FM Approved pallets are protected like wood ^[1].

Outdoors, DS 8-24 sets the distance between the stack and the building according to the exposed wall ^[1]:

Exposed wall	≤50 pallets, wood or FM Approved	≤50 pallets, plastic	51-200 pallets, wood or FM Approved	51-200 pallets, plastic	>200 pallets, wood or FM Approved	>200 pallets, plastic
Combustible	4.5 m	9 m	12 m	24 m	27 m	45 m
Non-combustible	3.7 m	4.5 m	9 m	12 m	15 m	30 m
1-hour rated	1.2 m	2.4 m	3.7 m	7.4 m	6 m	12 m
2-hour rated	1 m	2 m	3 m	6 m	4.5 m	9 m
4-hour rated	1 m	1 m	1 m	1 m	1 m	1 m

With a 4-hour wall, the 1 m is only there for access ^[1].

Diagram of outdoor idle pallet distances from a combustible wall according to FM DS 8-24 — In front of a combustible wall, above 200 pallets: 27 m for wood and 45 m for non-certified plastic.

United States: NFPA 13 and the International Fire Code

NFPA 13, 2025 edition, section 20.17.2.1, raises the class of commodities stored on plastic pallets ^[3]:

Pallet	Effect on commodity class
Unreinforced PP or HDPE	+1 class
Reinforced PP or HDPE	+2 classes
Other polymers	normally +2 classes, unless specifically tested
Listed and tested pallet	can be treated like wood, in some cases

Source: ^[3].

Two extra classes weigh heavily on the system. In the ICC article's example, the two-class increase required by the International Fire Code forces the system to deliver about 55% more water than the original design ^[2]. Idle pallets are a high-hazard commodity and can trigger high-piled storage rules from about 1.8 m (6 feet) in height ^[3].

Diagram of the NFPA 13 commodity class increase with unreinforced and reinforced plastic pallets — NFPA 13: one commodity class up with unreinforced plastic pallets, two with reinforced ones.

Europe: VdS CEA 4001 and the HHS class

In Europe many insurers use the VdS CEA 4001 rules. According to the position paper of a German association of plastics processors (March 2021), under point K.7.1 plastic load carriers fall into category IV (HHS4). Category III (HHS3) is allowed only for single-wall, water-permeable containers ^[4].

That paper deals mainly with containers and crates; pallets appear in a separate section, as part of the packaging risk ^[4]. For a pallet, then, ask your insurer or fire engineer for the class. FM Data Sheet 8-34 also sets a requirement for containers: at least 30% drainage area within 13 mm of the bottom ^[4].

Fire-retardant additives: what they do and what they don't

Many data sheets describe pallets as "self-extinguishing" or "fire retardant". According to the same industry paper, flame retardants shift the ignition temperature but leave the heat of combustion, and therefore the fire load, unchanged ^[4]. The paper lists other drawbacks: lower toughness, harder recycling, more harmful emissions. For these reasons the manufacturers in the working group normally do not use them ^[4].

Plastic pallets in a warehouse with ceiling sprinklers and a sign with the questions for the insurer — Fire retardant does not mean certified: for the sprinkler system, FM 4996 or UL 2335 is what counts.

What your system needs is the result of a full-scale test. An additive does not replace an FM or UL certificate.

Italy: who decides

We have found no Italian technical rule dedicated to plastic pallets. In practice the decision lies with the fire safety designer, through the risk assessment for the activity, and with the insurer, which may ask you to apply FM or VdS rules. If the warehouse already has sprinklers, switching from wood to plastic can change the hazard class and require an upgrade.

Checklist before you switch from wood to plastic

Ask your supplier whether the model is FM Approved or UL 2335 listed, with the certificate and the exact code. Put it in writing in your purchase specification.
Send the data sheet to your insurer and fire engineer before you order.
Calculate the fire load with the real weight of the pallets, loaded and empty.
Keep idle pallet storage separate, indoors and outdoors, with the DS 8-24 distances ^[1].
Do not rely on additives: ask for a test result ^[4].

For storage at height in pallet racking, see the guide to rackable plastic pallets and the one on pallets for automated warehouses. The full comparison with wood, including costs and carbon footprint, is in plastic or wood; materials and weights in plastic pallet materials. If you also store pallet boxes, the VdS rules for containers are summarised in the guide to plastic pallet boxes.

Frequently asked questions

Does a plastic pallet burn more than a wooden one?

Per kilo, yes: polypropylene releases 40-46 MJ/kg, wood 17-22 MJ/kg, so about twice as much. Per pallet it depends on the weight: a 16 kg plastic pallet holds more energy than a 10-20 kg wooden pallet, while a 6 kg lightweight one holds about as much as wood. That is why fire rules treat plastic more strictly, except for FM- or UL-certified pallets.

What does FM Approved mean on a plastic pallet?

It means the model has passed the FM 4996 test: eight stacks of pallets about 1.2 m high, set alight and controlled with a water density of 5.9 mm/min within 10 minutes. According to FM Data Sheet 8-24, an FM Approved pallet is stored and protected like a wooden pallet. The approval covers the individual model, not the manufacturer's whole range.

Do fire-retardant pallets solve the sprinkler problem?

Not on their own. According to a technical paper by a German trade association (2021), flame retardants raise the ignition temperature but leave the heat of combustion and the fire load unchanged. What counts is the result of a test such as FM 4996 or UL 2335, not the presence of the additive.

Can I store empty plastic pallets outdoors near the building?

Generally yes, but further away than wood. FM Data Sheet 8-24 gives, in front of a combustible wall, 9 m for a stack of up to 50 plastic pallets against 4.5 m for wood or FM Approved pallets, and 45 m against 27 m above 200 pallets. In front of a wall with 4-hour fire resistance, 1 m is enough for all. The distances for your site are set by your fire engineer and your insurer.

In Italy, who decides whether I can use plastic pallets in a sprinklered warehouse?

The fire safety designer decides, based on the risk assessment for the activity, together with the insurer, which may apply its own technical rules such as FM or VdS. Before you change pallets, give them the model's data sheet and any FM Approved or UL certificate.

Sources

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