Published
by Rogers Corporation
Elastomeric Material Solutions
Battery energy storage systems, commonly referred to as BESS, play a critical role in renewable energy integration, backup power, and grid stability. As these systems scale in size and deployment, fire safety has become one of the most closely scrutinized aspects of their design.
Two standards now dominate BESS fire safety discussions: UL 9540 and UL 9540A.
UL 9540 is the system-level safety standard for energy storage systems, while UL 9540A provides a method for evaluating thermal runaway and fire propagation behavior. Neither standard certifies individual materials such as foams. However, because both evaluate system behavior, they strongly influence how engineers approach material selection inside BESS enclosures.
As a result, many design teams specify UL 94 V-0 rated foams for gaskets, gap fillers, and enclosure pads as a risk-reduction measure. While UL 9540A does not mandate material-level certifications, using self-extinguishing foams helps limit the potential contribution of materials during system-level fire testing.
UL 9540 evaluates the overall safety of an energy storage system, including:
A UL 9540 listing is typically required for BESS installations to be approved by Authorities Having Jurisdiction (AHJ).
UL 9540A evaluates thermal runaway and fire propagation behavior under controlled conditions. Testing:
These evaluations are conducted at accredited laboratories and are commonly reviewed during permitting. Failing UL 9540A testing can result in redesigns, retesting, and significant project delays.
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Because UL 9540A testing is complex, time consuming, and costly to repeat, engineers often reduce risk earlier in the design process by making safe material choices for soft components.
Common reasons include:
Even though UL 9540A does not explicitly require material certifications, many BESS programs treat UL 94 V-0 as a baseline expectation for foams and gaskets.
In BESS assemblies, soft materials are commonly required to manage tolerances, vibration, and sealing. Typical applications include:
In these applications, UL 94 V-0 foams can help balance mechanical performance with fire safety expectations.
| Standard | Level Tested | Focus | Why It Matters to Engineers |
|---|---|---|---|
| UL 9540 | Complete system | Electrical, mechanical, enclosure, and code compliance | Required listing for most BESS installations under NFPA 855 and the International Fire Code. Supports Authority Having Jurisdiction (AHJ) approval. |
| UL 9540A | System under fire conditions (Cell → Module → Unit → Installation) | Thermal runaway and fire propagation | Evaluates whether failure propagates through the system. Results influence permitting, layout, and mitigation strategies. |
| UL 94 V-0 | Material (foams, plastics, elastomers) | Vertical flammability and self-extinguishing behavior | Guides material selection. Using V-0 materials helps reduce risk during UL 9540A system-level fire testing. |
PORON 40V0 polyurethane foam aligns with common BESS material requirements:
In applications where extreme temperature stability or outdoor weathering resistance are not required, PORON 40V0 material can be a practical alternative to silicone-based materials. A Rogers Sales Engineer can help evaluate suitability for specific BESS designs.
UL 9540 and UL 9540A define fire safety expectations for BESS at the system level. While these standards do not certify individual materials, reliable material selection helps reduce risk during system-level fire testing.
Using UL 94 V-0 foams for gaskets, gap fillers, and cushioning materials helps limit the contribution of soft components during UL 9540A evaluation and supports reliable long-term performance in modern BESS designs.
Request a sample of PORON 40V0 foam to evaluate it for your next energy storage project.
Published on Feb 04, 2026
