UL 9540A 2019-11 PDF

Full title and description

ANSI/CAN/UL 9540A:2019 — Test Method for Evaluating Thermal Runaway Fire Propagation in Battery Energy Storage Systems. This document is a UL consensus test method that defines procedures and acceptance criteria for inducing thermal events at cell, module, unit and installation scales to evaluate fire, smoke, gas and explosion hazards and to inform required fire‑protection and installation measures for stationary battery energy storage systems (BESS).

Abstract

UL 9540A provides a stepwise, practical test methodology to determine whether battery cells, modules, units or complete installations can undergo thermal runaway and, if so, how fires or explosions may propagate through the energy storage system or to adjacent equipment and structures. The results are used to guide separation distances, ventilation and suppression strategies, code interpretations and installation requirements referenced by building and fire codes and standards.

General information

• Status: Originally published 2019; later editions published (see FAQ). The 2019 edition has been incorporated into ongoing revisions and is listed as superseded by the 2025 edition in standards registries.
• Publication date: November 2019 (Edition 4 published 11/12/2019).
• Publisher: Underwriters Laboratories (UL), issued as a joint ANSI/CAN/UL consensus Test Method.
• ICS / categories: Energy and environmental protection / fire safety categories (examples shown in registries: 13.220; 27.100; 29.220).
• Edition / version: Edition 4 — 2019 (commonly referenced as UL 9540A Ed. 4‑2019 / ANSI/CAN/UL 9540A:2019).
• Number of pages: Approximately 60 pages (PDF editions sold through standards distributors list ~60 pages for the 2019 edition).

Scope

The Test Method determines whether a given battery technology or assembled energy storage system can undergo thermal runaway and characterizes the fire and explosion hazard behaviour across staged test levels (cell → module → unit → installation). Data from the tests support decisions on required separation distances, ventilation, fire suppression, enclosure design and emergency response planning for installations subject to building and fire codes and standards. The scope explicitly ties test results to code and installation guidance such as NFPA, IFC and related standards.

Key topics and requirements

• Four hierarchical test levels: cell‑level, module‑level, unit‑level and installation‑level examinations with pass/transition criteria that determine whether higher‑scale testing is required.
• Procedures to induce thermal runaway and to measure heat release, flaming, projection of burning material, overpressure/explosion potential, toxic and flammable gas generation, and temperature rise on adjacent targets.
• Criteria for containment or propagation (e.g., whether thermal runaway is contained within a module or unit, whether flaming extends beyond the unit, and target temperature limits used to assess spread).
• Guidance for reporting test configurations, instrumentation, and interpretation of results for application to installation design, separation distances and emergency planning.
• Use of results to inform compliance with installation codes (examples: NFPA 855, IFC, NFPA 1, NEC/NFPA 70) and to support manufacturer installation instructions.

Typical use and users

Manufacturers of battery cells, modules and packaged energy storage systems; testing laboratories and third‑party evaluators; code authorities and AHJs (Authorities Having Jurisdiction); utilities and project developers; insurers and fire protection engineers. Typical uses include product development and selection, regulatory compliance, site design (setback/venting/suppression), and risk assessment for commercial, utility and residential BESS installations.

Related standards

Commonly referenced standards and documents used with UL 9540A include UL 9540 (Safety standard for Energy Storage Systems and Equipment), NFPA 855 (Installation of Stationary Energy Storage Systems), International Fire Code (IFC), NFPA 1, NEC (NFPA 70) and other national/local codes and installation standards that rely on test data to set installation requirements. UL 9540A is explicitly referenced in several of these codes and in UL 9540 guidance.

Keywords

UL 9540A, thermal runaway, battery energy storage systems, BESS, fire propagation, module testing, unit testing, installation testing, fire safety, test method, NFPA 855, IFC, UL test method.

FAQ

Q: What is this standard?

A: UL 9540A is a UL consensus Test Method (ANSI/CAN/UL 9540A:2019, Edition 4‑2019) for inducing and evaluating thermal runaway and its potential to propagate fire or explosion within and beyond battery energy storage systems.

Q: What does it cover?

A: It defines staged test procedures (cell, module, unit, installation) and measurement/reporting requirements to characterize heat release, flaming, gas generation, projection of burning material and overpressure to inform installation safety measures, separation distances and fire protection strategies.

Q: Who typically uses it?

A: Battery and BESS manufacturers, test labs, code officials, engineers, developers, utilities and insurers use UL 9540A data to evaluate product safety, support installations, and meet code or permitting requirements.

Q: Is it current or superseded?

A: The 2019 edition (Ed. 4‑2019) remains an important published edition, but standards registries list a subsequent revision published in 2025 (ANSI/CAN/UL 9540A:2025). Users should verify which edition is referenced by their AHJ or project specification; many jurisdictions and manufacturers are migrating to the later edition where adopted.

Q: Is it part of a series?

A: Yes — UL 9540A is a companion test method to UL 9540 (the safety standard for Energy Storage Systems and Equipment) and is used alongside installation and electrical codes (e.g., NFPA 855, IFC) to determine safe installation requirements for BESS.

Q: What are the key keywords?

A: Thermal runaway, fire propagation, energy storage, BESS testing, cell/module/unit/installation tests, gas analysis, fire hazard, UL 9540A, NFPA 855.