UL 9540A
Test Method for Evaluating Thermal Runaway Fire Propagation in Battery Energy Storage Systems
Also written as ANSI/CAN/UL 9540A
- Issuing body
- UL Standards & Engagement
- Current edition
- 6th edition
- Published
- 2026-03-13
- Last verified
- 2026-08-06
What it covers
Not a pass or fail certification but a test method. It characterizes what happens when a cell is driven into thermal runaway: whether the failure propagates to neighboring cells, modules or units, what gases are released, and how heat and flame move through the installation. The resulting data is what fire protection engineers and authorities use to justify separation distances and explosion control decisions under NFPA 855.
Editions
- 6th edition In force 2026-03-13
The large-scale test section was rewritten to align with the 2026 edition of NFPA 855, and the unit-level test is no longer required for non-residential installations. Testing continues to be offered against the fifth edition during the transition.
- 5th edition Superseded 2025-03-12
- 4th edition Superseded
Next edition & pipeline
Official source
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View UL 9540A at UL Standards & Engagement ↗