The future of green energy and decarbonization relies heavily on energy storage systems (ESS). Storage technologies are advancing rapidly, and UL Solutions helps support safety throughout this evolution. By participating in standards panels and industry working groups, we help gather all relevant perspectives, build consensus, create economies of scale, and bring clarity to safety regulations. This Q&A was created to address questions in the market while maintaining our history of transparency and support.
- What are the current installation codes and standard requirements for ESS in the US related to fire and explosion testing?
The 2023 edition of NFPA 855 and the 2024 edition of the International Fire Code require fire and explosion testing to be conducted in certain situations. Both editions reference that such testing shall be conducted on a representative ESS in accordance with UL 9540A, the Standard for Test Method for Evaluating Thermal Runaway Fire Propagation in Battery Energy Storage Systems.
- What is the fire and explosion test method specified in the 2023 edition of NFPA 855?
UL 9540A is the test method specified in the 2023 edition of NFPA 855 and the 2024 edition of the International Fire Code. UL 9540A is also specified in Annex G of the 2023 edition of NFPA 855.
- What fire and explosion test method will the 2026 edition of NFPA 855 specify?
UL Solutions experts, fire officials and industry stakeholders are actively drafting stricter fire and explosion testing protocols in the upcoming 2026 edition of NFPA 855. The current draft specifies that fire testing must be conducted in accordance with UL 9540A and, in certain instances, incorporate large-scale fire testing.
- Will the 2026 edition of NPFA 855 reference any test method other than UL 9540A?
UL 9540A is the only fire and explosion testing method that will be referenced in the 2026 edition of NFPA 855.
- What are the updates to the latest edition of UL 9540A published on March 12, 2025?
The latest edition of UL 9540A covers key improvements that serve to streamline testing and drive towards consistency among test labs when conducting this test program. Primary changes consist of the following:
- Adding definition for thermal runaway propagation and clarify the criteria for establishing cell to cell propagation.
- Specifying thermocouple locations and adding option for a continuous thermal ramp for the Cell Level Test.
- Updating Module Level Performance Criteria to include a temperature limit for the module casing.
- Replacing the NFPA 286 fire test room with an instrumented wall for the Unit Level Test for residential BESS.
- Requiring the inclusion of test summaries from previous level tests in Module, Unit, and Installation Level Test reports.
- Introducing test methods for high-temperature, lead acid, and nickel cadmium batteries, and refine the test method for flow batteries.
- Enhancing unit level testing protocols for Rooftop and Open Garage installations.
- Permitting the Use of Gardon heat flux gauges for the Unit and Installation Level Tests.
- Implementing the use of flame ionization detection to measure total hydrocarbons as well as hydrogen measurements for the Unit and Installation Level Tests.
- Will UL 9540A address large-scale fire testing after the release of the 2026 edition of NFPA 855?
UL 9540A will evolve during the coming months to address large-scale fire testing criteria in NFPA 855. A dedicated task group within the UL 9540A Technical Committee has been diligently working the last year on development of a test method to address the increased demand for robust fire and explosion testing scenarios.
- How soon will the large-scale fire testing be incorporated in UL 9540A?
The technical committee is convening on April 29, 2025 to discuss the proposed large-scale fire test method and ballot voting is anticipated soon after.
- Can test methods other than UL 9540A be used for ESS large scale fire and explosion testing?
The current and next edition of NFPA 855 specify that UL 9540A is the required test method for ESS installation. In certain instances, ESS installations may require additional large-scale testing. Organizations may turn to alternative test methods for large-scale testing. However, these test methods are not widely accepted and should be considered on a case-by-case basis.
- Does UL Solutions offer large scale fire testing today?
Yes, in addition to being a leader in delivering UL 9540A test reports, UL Solutions can perform large scale fire testing.
- Where can UL Solutions conduct large-scale fire testing?
UL Solutions offers large-scale fire testing out of several facilities in the US, China and Korea.
Large batteries present unique safety considerations, because they contain high levels of energy. We remain committed to helping battery innovators enhance energy storage capacity with services to support greater safety, performance and reliability.
Get connected with our team
Learn more about ESS testing and certification with UL Solutions.