UL Solutions announced enhanced large-scale fire testing for battery energy storage systems (BESS) on April 23 2026 to provide code authorities and fire professionals with real-world information regarding battery fires.
The safety science organization conducts these tests according to the sixth edition of ANSI/CAN/UL 9540A – the Standard for the Test Method for Evaluating Thermal Runaway Fire Propagation in Battery Energy Storage Systems.
The updated method expands guidance for installation-level testing to replicate how fire starts inside an enclosure and impacts nearby equipment.
Thermal runaway is a battery failure condition where overheating causes the release of flammable gases and potential ignition.
Understanding this process at full installation scale is critical for evaluating safety risks.
Wesley Kwok, vice president and general manager of the Energy and Industrial Automation group at UL Solutions, said: “Battery energy storage systems are being deployed at larger scales and closer to where people live and work.
“This testing gives authorities and fire departments practical data they can use to evaluate layouts, separation distances and fire protection strategies with greater confidence.”
UL Solutions initiates a fire within a BESS enclosure during testing to observe development under realistic installation conditions.
The process examines if fire spreads between battery units or ignites nearby structures.
Testing also evaluates how ventilation and gas release influence fire behavior.
The performance of active and passive fire protection features is assessed when exposed to battery fires.
Test configurations mirror real installations such as outdoor containerized systems and indoor battery rooms.
Standardized setups include sites where multiple enclosures are grouped or stacked to ensure results remain relevant.
Findings are documented in detailed reports for code authorities to evaluate installation proposals and review alternative design approaches.
Robert Sapien, Jr., fire chief of the City of San José Fire Department, explained: “As communities expand their use of battery energy storage, we need to understand how these systems behave in a real emergency.
“Large-scale fire testing gives us the data we need to plan our response and protect both firefighters and the public.
“The insight gained is essential to adopting these systems safely.”
Designers can use the test information to develop risk-informed layouts and address permitting concerns early in the design process.
Fire departments use the findings for hazard assessments and pre-incident response strategies.
