UL 2335: fire tests of storage pallets
UL 2335, Fire Tests of Storage Pallets, tests how pallets contribute to fire in idle, palletized and rack storage protected by NFPA 13 sprinklers. Plastic pallets listed to UL 2335 or FM 4996 are treated like wood when sizing sprinklers; unlisted plastic raises the commodity class.
Fire codes treat unlisted plastic pallets as a bigger fire hazard than wood, and sprinkler systems in most warehouses are designed around wood pallets. UL 2335 is how a plastic pallet proves it will not overwhelm those sprinklers. Its title is Fire Tests of Storage Pallets. It is published by UL Standards & Engagement as an ANSI/UL standard; the most recent revision we could confirm is dated 2022.
What does UL 2335 cover?
UL 2335 contains test methods and requirements for the fire growth performance of pallets:
- in idle storage (stacks of empty pallets), and
- when storing commodities in palletized and rack storage arrangements,
in buildings protected by sprinkler systems installed to NFPA 13. The results show whether a pallet's fire contribution is comparable to wood under those conditions. Listed pallets carry the UL mark and appear in UL's certification directory with the conditions of the listing.
Why UL 2335 matters: the fire code
The International Fire Code, as adopted in state and local fire codes, and NFPA 13 both treat plastic pallets as a higher hazard than wood unless they are listed. The key rule, which appears in adopted fire codes, is that plastic pallets listed and labeled to FM 4996 or UL 2335 are treated as wood pallets when determining required sprinkler protection.
| Pallet | Effect on sprinkler design (NFPA 13) |
|---|---|
| Wood | Baseline |
| Plastic, listed to UL 2335 or FM 4996 | Treated as wood |
| Plastic, unlisted, unreinforced | Commodity classification raised by one class |
| Plastic, unlisted, reinforced | Commodity classification raised by two classes |
Raising the commodity class can mean higher sprinkler density, in-rack sprinklers, lower storage heights or separate storage rooms for idle pallets. Upgrading sprinklers can easily cost more than the price difference between listed and unlisted pallets. Your fire protection engineer, the authority having jurisdiction and your insurer decide what applies in a given building.
How plastic pallets pass
Makers usually reach a UL 2335 or FM 4996 listing with a fire-retardant resin formulation, sometimes with design changes. That has side effects buyers should know:
- Fire-retardant pallets usually cost more and can weigh more.
- Fire-retardant additives can affect recyclability or food-contact status; ask for both a UL listing and a food-contact letter if you need both.
- A listing applies to a specific model and formulation. A "UL 2335" claim for a different color, resin or recycled content needs checking in the certification directory.
Pooled plastic pallets are often listed. iGPS, for example, states its 48 × 40 plastic pallet is UL 2335 listed. See plastic pallets and the plastic pallet buying guide.
How it relates to other standards
| Standard | Relationship |
|---|---|
| FM 4996 | FM Approvals' equivalent classification for idle plastic pallets; codes accept either |
| NFPA 13 | Sprinkler design standard whose commodity classes UL 2335 feeds into |
| International Fire Code | Storage rules for idle pallets and the "treat as wood" provision |
| ISO 8611 / ASTM D1185 | Load ratings; a fire listing says nothing about strength |
| FSMA sanitary transportation | Food safety, a separate question from fire |
When should a buyer cite UL 2335?
Cite it whenever plastic pallets will be stored indoors in a sprinklered building, which covers most distribution centers, retail back rooms and 3PL warehouses. It matters most for:
- idle pallet storage, where stacks of empty plastic pallets are a concentrated fire load,
- high-bay rack storage,
- closed-loop plastic pallet programs in food, beverage and pharmaceutical plants.
How to reference it on a spec sheet
- "Plastic pallet listed to UL 2335 (or FM Approved to FM 4996) for [idle storage / rack storage]; listing number to be provided."
- "Fire-retardant formulation must not change without re-listing and buyer approval."
- "Food-contact letter of compliance required" (if applicable).
For the wider picture, including idle pallet storage limits for wood, see pallet fire safety.
Frequently asked questions
Do I need UL 2335 plastic pallets?
If you store plastic pallets, loaded or idle, in a sprinklered building, a UL 2335 or FM 4996 listing usually lets them be treated as wood for sprinkler design. Without it, the fire code or NFPA 13 may require more sprinkler protection or limits on storage. Ask your fire protection engineer or insurer.
Do wood pallets need UL 2335?
No. Wood pallets are the baseline the fire codes are written around. UL 2335 exists to show that a plastic (or other) pallet performs no worse than wood.
What is FM 4996?
FM Approvals' standard for classifying idle plastic pallets as equivalent to wood pallets. Fire codes accept either an FM 4996 approval or a UL 2335 listing.
Does a UL 2335 listing mean the pallet will not burn?
No. It means the pallet's fire contribution was tested and found acceptable for the stated storage conditions compared with wood. Plastic and wood pallets both burn.
Sources and references
- UL 2335, Fire Tests of Storage Pallets (UL Standards & Engagement)
- NFPA 13, Standard for the Installation of Sprinkler Systems (NFPA)
- International Fire Code, pallet storage provisions (ICC), as adopted in state fire codes
Related
- GlossaryUL 2335UL 2335 is the UL standard for fire tests of storage pallets. Plastic pallets listed to UL 2335, or approved to FM 4996, can be treated as equivalent to wood pallets when fire codes set sprinkler protection, while unlisted plastic pallets can raise the required protection.
- GuidesPallet fire safety: idle pallet storage, NFPA 13, fire codes and UL 2335Stacks of idle pallets burn fast and hot, so NFPA 13 and fire codes treat them as a special hazard. Store them outdoors or in a detached building where possible; indoors they need specific sprinkler protection. Unlisted plastic pallets count as a higher hazard than wood. Confirm with your AHJ.
- TypesPlastic pallets: types, materials, load ratings and how to buy themA plastic pallet is a molded or fabricated pallet made from HDPE or polypropylene. Types range from light nestable pallets (about 14–30 lb) to reinforced rackable pallets (about 35–70 lb). They are washable, ISPM 15 exempt and long-lived, cost several times more than wood, and carry three separate load ratings.
- GuidesPlastic pallet buying guide: styles, resins, ratings and costChoose a plastic pallet by how it is handled and stored: nestable for cheap one-way use, stackable for floor stacking, rackable for open-beam racking. Compare static, dynamic and racking ratings only when the test standard and support match. New US prices run about $40–200 (2026 estimates).
- ComparisonsPlastic vs wood pallets: cost, strength and when to use eachChoose wood when you need the lowest price, a custom size, easy repair or one-way shipping. Choose plastic when pallets run in a closed loop for many trips, when hygiene and washability matter, when you need consistent dimensions for automation, or to avoid ISPM 15 treatment on exports.
- TypesRackable plastic pallet: runners, reinforcement and racking ratingsA rackable plastic pallet is designed to sit in open-beam racking with nothing underneath. It has runners (3, 5 or 6) or a perimeter or cruciform base, often with steel reinforcement. Racking ratings for 48 × 40 in models are typically about 1,500–4,400 lb, valid only at the tested span and orientation.
- IndustriesPallets for e-commerce, fulfillment and 3PL warehousesE-commerce and 3PL warehouses mostly receive 48 × 40 in four-way pallets and publish receiving rules on grade, height, weight, wrap and labels. For Amazon FBA, 40 × 48 in four-way pallets, 72 in and 1,500 lb are widely cited limits. Used Grade A or B pallets usually meet inbound rules.
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Last reviewed 2026-09-24. 672 words.