Applications: Stationary Energy Storage

Large Scale Fire Testing LSFT Became an Established Testing Requirement in 2025 A change in the 2026 Edition of NFPA 8551 supplanted Edition 5 of UL 9540A as the de-facto Large Scale Fire Test. However, consensus was reached in August of 2025 on a new revision that will bring the UL 9540A test method back into alignment with the intent of NFPA 855 and the model fire codes that reference it.2

Standard

Focus

What

Why

UL 9540A Ed. 5 Edition 6 publication target March 31, 2026

Thermal runaway behavior, fire and gas hazards, module/unit propagation

Internal propagation, gas composition, ignition susceptibility, flame/heat characteristics

To understand internal failure mechanics and gas hazards.3

Large Scale Fire Testing (per 2026 NFPA 855, no specific standard referenced)

Fully developed unit-level fire + external exposure risk.

Real-world fire spread, heat flux to exposures, suppression performance, structural risks

Required to determine separation distances, suppression design, and installation safety4

UL 9540B Outline of Investigation

Residential ESS fire propagation

Fire severity and spread from a failure of an ESS in a residential setting.

Addresses risk to occupants by evaluating the “fire propagation characteristics of residential BESSˮ5

CSA C800 Note: CSA TS 800 interim specification now incorporated into this document.)

Reliability & QA

ESS reliability under extreme external abuse conditions

Establishes BESS behavior when subjected to abuse resulting in a developed fire condition.6 Developed to supplement UL 9540A Edition 5.

Consensus revisions provide data required to determine separation distances, suppression design, and installation safety

Source: NFPA Standards Council Decision, UL Standards Activity, UL 9540A, Edition 5. See Scope, NFPALink®, UL 9540B, See Scope, CSA Group

Extracted from the PDF; charts and images may read imperfectly.