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The 2026 edition of NFPA 855 contains numerous updates to improve the fire safety of BESS installations

The , contains many new changes, including broader use of Hazard Mitigation Analysis (HMA) and new provisions addressing large-scale fire testing, emergency response planning, fire protection strategies, and explosion hazards for most battery energy storage system (BESS) installations unless explicitly exempted. The changes are expected to affect how manufacturers and system designers, owners, and permitting authorities approach system design, safety validation, and project permitting.

"The revised NFPA 855 framework strengthens expectations for formal safety analysis, emergency planning, and the role of qualified professionals in evaluating BESS hazards."

Hazard Mitigation Analysis becomes the default requirement

In , an HMA was required only under specific circumstances — for example, when an installation exceeded certain maximum stored-energy limits. Projects that remained below those limits could often proceed without a formal hazard analysis. The 2026 edition removes that threshold-based approach, making an HMA a standard part of the safety evaluation for most BESS installations unless explicitly exempted in technology-specific chapters.

This change significantly alters how manufacturers and system designers, installation owners, and permitting authorities evaluate BESS safety. Project teams should now anticipate that an HMA will be required as part of the design and approval process and incorporate it early in project planning.

What does Hazard Mitigation Analysis evaluate?

, an HMA may include evaluating the consequences, survivability, and reliability of the following:

• Initiation and propagation of thermal runaway events
• Generation and dispersion of hazardous gases
• Potential for deflagration or explosion
• Evaluation of detection, suppression, and ventilation systems
• Separation, containment, or compartmentation strategy defects

These analyses often rely on a combination of detailed design review, engineering modeling, fire testing data (such as from UL 9540A and CSA C800-compliant testing), and performance-based safety assessments to demonstrate that the proposed system can operate as designed.

Expanded explosion control and prevention requirements

The 2026 edition of NFPA 855 also introduces significant updates related to explosion control and prevention. These changes place emphasis on managing hazardous gases generated during thermal runaway events and incorporate more prescriptive requirements for system design, validation, and performance.

The updated standard requires that BESS installations incorporate an explosion control and prevention system designed and implemented in accordance with NFPA 69 or a performance-based alternative supported by installation-level fire and explosion testing and engineering evaluation. 

In contrast to previous editions, NFPA 68 deflagration venting systems are no longer permitted as a primary explosion control strategy, reflecting a shift toward active prevention and control of hazardous gas accumulation. 

The standard also introduces enhanced requirements for combustible concentration reduction (CCR) systems, which are intended to limit the accumulation of hazardous gases during a thermal runaway event. These systems must be designed to remain operational during failure scenarios and are expected to address: 

• Evaluation of gas composition and volume data derived from testing, such as UL 9540A
• Partial volume deflagration scenarios
• Hazardous gas migrations between interconnected ESS units

These additional requirements further reinforce the importance of hazard evaluation, including Hazard Mitigation Analysis, in assessing the role of hazardous gases and validating mitigation strategies.

Implications for BESS developers and project teams

NFPA 855 (2026) strengthens the direct integration of hazard assessments into the design justification for energy storage projects. The standard also reinforces expectations that these analyses be conducted or directed by qualified professionals. As a result, organizations developing or deploying BESS may need to:

• Integrate hazard analysis earlier in the project lifecycle
• Coordinate more closely with Authorities Having Jurisdiction (AHJs) during permitting
• Apply fire testing data when evaluating fire safety and mitigation strategies
• Ensure that emergency planning and responder coordination align with updated code expectations

Supporting compliance with NFPA 855 (2026)

Evaluating BESS fire and explosion hazards typically requires multidisciplinary expertise spanning battery technology, fire safety, gas dispersion modeling, explosion hazard analysis, and energy storage system design. 

As energy storage deployments continue to expand globally, the 2026 update to NFPA 855 reflects increasing emphasis on performance-based safety and hazards evaluation using large-scale fire testing for BESS projects. Organizations evaluating new or existing installations may benefit from reviewing current designs and permitting strategies to support alignment with the updated code requirements.