Large-scale fire testing and NFPA 855
Maintaining safety in the battery industry involves applying existing knowledge and services to new technology while also developing a deep understanding of innovative products, identifying the need for new services and responding effectively to requirements intended to support a safer future.
To help maintain battery energy storage system (BESS) safety, the 2026 edition of NFPA 855 is anticipated to include a new annex with guidance on implementing a large-scale fire test (LSFT). Many installation codes and standards are also evolving to address modern energy storage applications, with some, including the International Fire Code (IFC), already introducing requirements aimed at modern energy storage system applications.
Download our white paper for clarification on NFPA 855 requirements for ESS installations.
Overview of large-scale fire testing
Large-scale fire testing involves igniting vented battery gases during a thermal runaway event to achieve a fire condition in the BESS. The objective is to determine how the BESS behaves under ignited (forced) fire conditions.
The flame spread, and in some cases, heat release, gas emissions and suppression system performance are monitored to evaluate the system’s prescribed separation distances and propagation potential to other BESS.
Why large-scale fire testing matters
As demands for energy storage systems grow, so do risks. Large-scale fire testing provides critical data that can help:
Support manufacturers’ installation and commissioning instructions
Inform whether the system and installation can contain or minimize fire spread
Protect surroundings from catastrophic failures
Why UL Solutions for UL 9540A testing
We leverage our network of global laboratories to provide large-scale fire testing of BESS and address all requirements in UL 9540A, the Standard for the Test Method for Evaluating Thermal Runaway Fire Propagation in Battery Energy Storage Systems. Tests at this scale require a fire event, necessitating advanced laboratory capabilities and subject matter expertise.
UL Solutions combines our residential and containerized battery energy storage capabilities with our extensive battery technology knowledge to help enable safer system designs and market confidence.
Download our guide to discover the key updates in UL 9540A:2025 that enhance testing methods and safety for battery energy storage systems against thermal runaway fire propagation.
Benefits of our services
UL Solutions is a global leader in safety science with decades of experience in fire testing, energy storage systems and regulatory compliance. Our experts offer:
Comprehensive services
We offer testing capabilities for the battery cell, module and unit levels as well as for containerized BESS within our network of laboratories.
Global reach
We can support your projects wherever they are deployed, with capabilities provided in North America, Asia and Europe.
Early engagement
We can be involved from the start to support complex, high-risk products that are outside the usual scope of work.
Proven expertise
Our technical expertise and market knowledge help you expand your understanding of compliance and safety. UL Solutions is trusted by global code authorities and aligns with the latest code requirements.
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Contact us today to learn how large-scale fire testing can support your path to compliance.
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