NFPA 855 - Battery Design

NFPA 855 is the primary standard and benchmark for the installation of Battery Energy Storage Systems (BESS) in North America, specifically designed to mitigate major risks such as thermal runaway, fire, and toxic gas release. It covers the design, installation, commissioning, and maintenance of various battery chemistries, including Lithium-Ion, Lead-Acid, and Flow Batteries.

Disclaimer: this is not a definitive guide, just an indication and it is important that you always go back to the source for legislation.

Current edition: 2026 Edition (previous: 2023 Edition). The 2026 Edition significantly expands scope and tightens several operational requirements — see “2026 Edition — Key Changes” below.

To ensure safety, NFPA 855 mandates several strict regulatory requirements and relies on a suite of third-party hardware certifications.

Key Regulatory Requirements under NFPA 855:

Location and Spacing (The 3-Foot Rule): BESS units must generally be separated by a minimum of 3 feet (0.9 meters) from one another and from surrounding walls or structures. The standard also defines maximum capacity thresholds (e.g., 20 kWh limits for individual Li-ion units) that automatically trigger specific safety protocols.
Fire Suppression and Detection: Because traditional fire sprinklers are often insufficient for battery fires, NFPA 855 mandates automatic fire-extinguishing systems, which are typically water-based to effectively cool the system and prevent the propagation of thermal runaway. It also requires gas detection systems in certain indoor setups to detect flammable “off-gases” prior to ignition, as well as explosion control (like deflagration venting) to manage dangerous pressure build-up.

The “Safety Trinity” Hardware Certifications: NFPA 855 relies on specific UL certifications to validate the safety of the equipment being installed:

UL 1973: Focuses on the battery module and pack, testing the cells for electrical, mechanical, and environmental abuse.
UL 9540: Evaluates the complete system integration, ensuring the batteries, Battery Management System (BMS), and inverters work safely together.
UL 9540A: A specific test method used to characterize thermal runaway fire behaviour. If a manufacturer wishes to safely reduce the mandated 3-foot separation distance, they are required to provide data from UL 9540A testing to prove a fire in one unit will not spread to adjacent units.

Operational and Emergency Planning:

Hazard Mitigation Analysis (HMA): Large systems or those placed in sensitive locations require an HMA. This analysis evaluates the consequences of a single-failure event to demonstrate that the installation can safely contain the hazard without threatening life or property.
Emergency Operations Plan (EOP): Facilities must supply their local fire departments with a dedicated EOP. This plan must detail how to safely shut down and de-energize the system, provide firefighting strategies tailored to the specific battery chemistry, and outline protocols for dealing with damaged or “hot” batteries after an event.

2026 Edition — Key Changes:

Hazard Mitigation Analysis (HMA) is now the default requirement for virtually all ESS installations within the standard’s scope, unless a later chapter specifies an exemption (e.g. traditional lead-acid or aqueous nickel-based batteries with a long, well-characterised safety history). Previously HMA applied to a narrower set of large or sensitive installations.
Expanded battery chemistry coverage: new non-lithium and alternative chemistries are explicitly addressed, including iron-air, nickel-hydrogen, hybrid supercapacitors, zinc-bromide, and lithium metal systems, alongside existing Li-ion and lead-acid coverage.
Thermal Runaway Propagation Prevention (TRPP) systems are newly required under Section 9.7.6.6: installations must incorporate an explosion control and prevention system designed to NFPA 69, or a performance-based alternative supported by installation-level fire and explosion testing and engineering evaluation.
Fire detection options widened: Section 14.3.2.1.2 now permits early fire detection using smoke detection, thermal imaging fire detection, or radiant energy detection, provided the system is installed to NFPA 72.
Tighter alignment with UL 9540A: the 2026 Edition’s large-scale fire test (LSFT) references align with the UL 9540A 6th Edition (published March 2026), which formally incorporated installation-level LSFT and added a large-scale deflagration test annex.
“Qualified Person” tightened: the definition is now explicitly tied to ESS-specific skills, knowledge and training, and safety training to recognise, avoid and mitigate ESS hazards — rather than generic electrical-equipment competence.

Global Standards Certifications for BESS

The Global Standards Certifications for BESS container based solutions is significant. As Battery Energy Storage Systems become critical to modern power infrastructure, compliance with international standards ensures safety, performance, and interoperability across components from cells to containerized systems.