In short
Lithium ion battery energy storage systems at AI data centers are regulated by a stack of standards, model codes, and federal rules. The core fire and installation standard is NFPA 855, which applies when stored energy exceeds 20 kilowatt hours for lithium ion chemistries. NFPA 855 It now requires a hazard mitigation analysis for most BESS installations under § 4.4, removing the previous stored energy thresholds, and it requires an explosion control and prevention system. NFPA 855 (2026) § 4.4 The International Fire Code and NFPA 1 adopt NFPA 855 by reference, and the electrical installation rules are in NFPA 70. U.S. model building and fire codes, including NFPA 855 and the International Residential Code, require stationary energy storage systems to be UL 9540 listed. NFPA 855, 2021 IRC Outside the building, federal transportation rules under 49 CFR and hazardous waste rules under the Resource Conservation and Recovery Act apply when batteries move or reach end of life. Operating and reporting duties also flow from OSHA’s Hazard Communication Standard and the Emergency Planning and Community Right to Know Act.
What are the core standards that apply to lithium-ion battery storage at AI data centers?
The starting point is NFPA 855, the National Fire Protection Association standard for stationary energy storage system installation. It sets the fire safety and building separation requirements that local authorities enforce. The standard was first published in 2020 and updated in 2023 and 2026, with each edition adding new requirements. NFPA 855, NFPA 855 (2020 edition), NFPA Journal, Energy storage industry analysis
NFPA 855 does not stand alone. Two model fire codes adopt it by reference. The International Fire Code, known as the IFC, has its own ESS provisions in Section 1207 that are largely harmonized with NFPA 855. IFC Chapter 12 The alternative model code, NFPA 1, does the same through Chapter 52. NFPA 1, Chapter 52 Which one governs your project depends on the edition the state or local jurisdiction has enacted, and those adoptions are not uniform across the country.
The electrical installation rules are in NFPA 70, the National Electrical Code. Article 706 governs energy storage systems that hold more than 1 kWh. NFPA 70, 2023 NEC 706.1
A parallel layer comes from the testing and listing standards. Under the UL system, an energy storage system must be listed to UL 9540, which covers the entire system. Inside that, the batteries themselves must meet UL 1973, and the cells must meet UL 1642. UL 9540, ESS standards summary Both the IFC and NFPA 855 require UL 9540 listing.
Finally, property insurers impose their own loss prevention requirements. FM Global publishes Data Sheet 5-32 for AI data center facilities and Data Sheet 5-33 for lithium ion battery energy storage systems. FM Global DS 5-32, FM Global DS 5-33 These data sheets are not laws, but lenders and carriers often require compliance as a condition of financing or coverage.
This stack creates a single compliance obligation. An AI data center operator must meet the locally adopted fire code, which requires meeting NFPA 855, which requires a UL 9540 listed system, installed per NFPA 70, and the operator’s insurer will likely overlay FM Global’s data sheets.
When does NFPA 855 apply to a battery system?
NFPA 855 applies based on the amount of stored energy, measured in kilowatt hours. The threshold depends on the battery chemistry.
| Battery chemistry | NFPA 855 applies when stored energy exceeds | Source note |
|---|---|---|
| Lithium ion, sodium nickel chloride, flow batteries | 20 kWh | NFPA 855 Table 1.3 |
| Nickel zinc, lead acid | 70 kWh (and no single string over 50 kWh) | NFPA 855 Table 1.3 |
Below these thresholds, NFPA 855 does not govern. That matters for smaller battery backup units distributed across server racks. However, once the cumulative energy in a space crosses the line, the standard applies to the installation.
The standard also imposes a hard capacity ceiling for lithium-ion chemistries. No more than 600 kWh of lithium ion stored energy may sit inside a single fire enclosure area, such as a dedicated battery room, though this limit does not apply to dedicated use buildings. NFPA 855 (2023) Lead acid and nickel based batteries have no equivalent limit. This means a large AI data center that needs megawatt hours of backup power from lithium ion batteries must split the storage across multiple fire separated rooms.
The International Fire Code separately requires a construction permit and an operational permit for stationary energy storage system installations. IFC § 1207.1.2
What are the key physical and fire protection requirements under NFPA 855 and the IFC?
Once NFPA 855 applies, the standard imposes a set of rules designed to contain a fire and protect people and the building.
Separation and barriers. Lithium ion battery cabinets must sit at least 3 feet from walls. NFPA 855 (2023) The IFC requires at least 10 feet between a battery energy storage system and an adjacent building, though exceptions can reduce that to 3 feet under specific conditions. IFC § 1207.8.3
Fire resistance of the battery room. When a lithium ion battery room is co located with data halls, the structure must carry substantial fire resistance ratings. Beams, columns, walls, and sealed penetrations need a 2 hour rating. Top and bottom floors and evacuation doors need 1.5 hours. Huawei/ITU white paper Under NFPA 855, the battery room must be separated from the AI data center equipment area by a fire rated wall, and lithium ion battery storage is limited to 600 kWh per fire area. NFPA Journal, NFPA 855 overview, NFSA analysis
Location limits. Lithium ion battery rooms must not be placed in a basement or semi basement. The lithium ion battery room shall not exceed 24 meters above ground, and if the height exceeds 24 meters the room must meet local fire rescue equipment conditions. Huawei/ITU white paper
Ventilation and water spray. The battery room must have emergency mechanical ventilation that exchanges air at least 12 times per hour. Huawei/ITU white paper A water spray fire extinguishing system must deliver at least 20 liters per minute per square meter. Huawei/ITU white paper The fire water storage must support at least 2 hours of operation, and a surrounding water source should sustain for at least 7 hours of continuous supply. Huawei/ITU white paper
Personnel response. The 2026 edition of NFPA 855 tells AI data center personnel plainly they must not attempt to approach or extinguish a battery energy storage system that is in alarm and showing visible fault signs such as sparks, arcs, flames, or gas plumes. They must evacuate, activate the emergency plan, and wait for emergency responders. No portable fire extinguisher is effective on a lithium ion battery fire. OCP Ready Requirements for ESS white paper § 12
How does the 2026 NFPA 855 edition change hazard mitigation and explosion control?
The 2026 edition significantly expanded hazard mitigation analysis and explosion control requirements. Exponent
The Hazard Mitigation Analysis, or HMA, was previously required only for installations that crossed certain stored energy thresholds. The 2026 edition removed those trigger points. Now an HMA is a standard requirement for most battery energy storage system installations, with only narrow technology specific exemptions. NFPA 855 (2026) § 4.4 The HMA may include evaluating thermal runaway initiation and propagation, hazardous gas generation and dispersion, deflagration and explosion potential, detection, suppression, and ventilation system performance, and separation, containment, or compartmentation strategy weaknesses. NFPA 855 (2026) § 4.4
Thermal runaway is a chain reaction inside a battery cell where rising temperature causes further reactions, releasing more heat, gases, and smoke. Temperatures can rise at a rate greater than 20°C per minute and can exceed 300 degrees Celsius. News analysis
When thermal runaway occurs in a contained space, the flammable gas can accumulate. A deflagration is a fast combustion wave driven by that accumulated gas. The 2026 NFPA 855 now requires an explosion control and prevention system that meets NFPA 69. It no longer permits deflagration venting under NFPA 68 as the primary explosion control strategy. Instead, a combustible concentration reduction system must keep the flammable gas concentration below 25 percent of its lower flammable limit. ACP overview
The 2019 APS battery storage facility explosion in Surprise, Arizona, drove many of these changes. A defective cell caused thermal runaway, gas built up inside a sealed container, and when first responders opened the door the accumulated gas exploded. Nine people went to the hospital. Mayfield Renewables, FirefighterNation The new rules are a direct response.
What fire suppression systems does FM Global recommend for AI data centers with lithium-ion batteries?
FM Global’s loss prevention recommendations go beyond the code minimums and are often required by insurers. They break the problem into two categories, namely battery backup units inside the data hall, and dedicated energy storage system rooms or outdoor containers.
For lithium-ion battery backup units distributed across the data hall, Data Sheet 5-32 sets a threshold of 20 kWh per rack. Below that limit, the area can be protected with quick-response sprinklers at a density of 0.2 gallons per minute per square foot, with a maximum sprinkler spacing of 12 feet and a demand area of 2,500 square feet. FM DS 5-32 Above that limit per rack, the system must be treated as an energy storage system under Data Sheet 5-33.
FM Global fully approves water mist systems for all areas of an AI data center, including equipment using lithium-ion batteries in distributed power systems, a position it reached in January 2023. Fire-TechInfo Clean agent systems alone, such as FM200 or Novec 1230, are not sufficient. Clean agents may temporarily knock down a flame, but they provide no cooling, so they cannot stop the thermal runaway reaction inside the battery cells. The fire can restart after the agent dissipates. News analysis
For larger, concentrated installations, Data Sheet 5-33 recommends designing the fire protection as automatic sprinkler protection with a density of 0.30 gpm per square foot over the room area, and recommends FM Approved off gas detection as one early intervention option. FM DS 5-33 §2.4.1, §2.5.3.3.1, OCP Ready ESS white paper
When returned, defective, off specification, or damaged lithium ion cells must be isolated outside the building or in a cut off room per FM Data Sheet 7-112 § 2.4.6. FM DS 7-112 § 2.4.6
How are lithium ion batteries transported to and from an AI data center?
The Pipeline and Hazardous Materials Safety Administration, PHMSA, regulates lithium ion battery transport under 49 CFR Part 173.185. A lithium ion battery that powers separate equipment, such as a UPS, is classified as UN3480 for transportation. 49 CFR 173.185, PHMSA Interpretation 22-0110
Shipments of UN3480 batteries are banned from passenger aircraft. On cargo aircraft, each standalone lithium ion battery shipped without equipment (UN3480) must be at 30 percent state of charge or less. PHMSA Lithium Battery Guide For cargo aircraft only, the net weight of lithium ion batteries per package is limited to 35 kilograms, measured by the battery weight alone, not the equipment weight. PHMSA Interpretation 22-0110 For ground transport, batteries of 300 watt hours or less may qualify for exceptions. 49 CFR § 173.185(c)
Packaging must prevent short circuits, damage from shifting, and accidental activation. Lithium cells or batteries must be placed in non metallic inner packagings that completely enclose the cells or batteries and separate them from contact with equipment, other devices, or electrically conductive materials. 49 CFR § 173.185(b) Since May 10, 2024, every lithium ion battery must be marked with its watt hour rating on the outside case. PHMSA Guide The lithium battery mark on the package must measure at least 100 millimeters by 100 millimeters, except a mark of 100 millimeters by 70 millimeters may be used when the package is too small for the larger mark. 49 CFR § 173.185(c)(3), PHMSA Lithium Battery Guide
These rules apply whenever an AI data center operator receives new batteries, ships defective ones back, or sends end-of-life batteries to a recycler.
How must end of life lithium ion batteries be managed under federal hazardous waste rules?
Lithium ion batteries removed from service are likely to exhibit hazardous waste characteristics for ignitability (code D001) and reactivity (code D003) under the Resource Conservation and Recovery Act, or RCRA. The Environmental Protection Agency recommends that businesses consider managing all their used lithium batteries as hazardous waste under the federal universal waste regulations. EPA lithium ion battery recycling FAQ
The universal waste program in 40 CFR Part 273 provides a streamlined process. Handlers do not need to use hazardous waste manifests, but they must send the waste only to another universal waste handler, a destination facility, or a foreign destination. 40 CFR Part 273 A large quantity universal waste handler may accumulate 5,000 kilograms or more of universal waste at any one time and may keep it on site for up to one year. 40 CFR 273.9, 40 CFR 273.35
The universal waste option is not available for batteries where the breakage or damage constitutes a breach in the cell casing. Those must be managed as fully regulated hazardous waste. EPA FAQ
The EPA is developing a new universal waste standard specifically for lithium batteries, separate from the existing general battery category, under RIN 2050-AH32. The rule remains at the proposal stage in the agency’s regulatory agenda, which projects a final rule in 2027. It had not been finalized as of this article. EPA Rulemaking, EPA webpage
A further legal question arises from the Battery Act of 1996, which preempts state law for the collection, storage, and transportation of used rechargeable batteries. Some lawyers argue this preemption could limit the EPA’s authority to modify universal waste standards for rechargeable lithium batteries in the states that the EPA has authorized to run their own RCRA programs. Law firm analysis That issue remains unresolved.
What reporting duties does an AI data center operator have under EPCRA and OSHA?
Storage of lithium-ion batteries in quantity can trigger chemical inventory reporting under the Emergency Planning and Community Right-to-Know Act, known as EPCRA. OSHA’s Hazard Communication Standard also applies.
OSHA has determined that lithium ion batteries are not articles under the Hazard Communication Standard because they can leak, spill, or break during normal use and in foreseeable emergencies. OSHA Letter of Interpretation This means the batteries are treated as hazardous chemicals. The operator must maintain a safety data sheet, or SDS, for the batteries, and must label them with hazard information under 29 CFR 1910.1200. 29 CFR 1910.1200(f)(1), (f)(6), (g)(1), (g)(8), OSHA letter of interpretation Several other OSHA provisions apply, including those for fire prevention plans, electrical safety, and personal protective equipment. The General Duty Clause imposes a broad safety obligation. OSHA Workers’ Rights
Under EPCRA, lithium-ion batteries are not articles and may require Tier II hazardous chemical inventory reporting. For hazardous chemicals that are not Extremely Hazardous Substances, the federal reporting threshold is 10,000 pounds present at the facility at any one time. EPA Tier II Reporting Guidance, EPA Hazardous Chemical Inventory Reporting, EPA EPCRA Guidance, 40 CFR 370.10 Some states and even counties impose lower thresholds. For example, Louisiana uses a 500 pound threshold, and the town of Gilbert, Arizona, has imposed its own lower limit. Trade press A large battery installation that holds tens of thousands of pounds of batteries will exceed the federal threshold.
If a thermal runaway event releases CERCLA hazardous substances above their reportable quantities, such as hydrogen fluoride or hydrogen cyanide, an immediate notification to the State Emergency Response Commission and the Local Emergency Planning Committee may be required. CERCLA/EPCRA If the release is fully contained on site with no off-site exposure, the notification to those bodies is not required, but the operator may still need to notify the National Response Center.
How do state and local fire codes apply these standards?
Code adoption is not uniform. The IFC and NFPA 1 are model codes, and each state, county, and city decides which edition to adopt and when. Most states are on the 2015 or 2018 cycles as of 2021, but the picture changes constantly. Mayfield Renewables This patchwork means the precise version of NFPA 855 that applies to a project, and whether it is the 2020, 2023, or 2026 edition, depends on the local adoption.
Virginia adopts the 2021 IFC. The statewide fire prevention code contains Chapter 12 Section 1207, which governs energy storage systems. Virginia SFPC Texas enforces the 2020 edition of NFPA 855 in areas under the State Fire Marshal’s jurisdiction. The Texas State Fire Marshal’s Office requires battery energy storage systems to have early warning fire detection, water based sprinklers or engineered alternatives, emergency operations plans, and regular inspection and maintenance. Texas SFMO Georgia adopts the International Fire Code statewide, and the 2024 IFC incorporates NFPA 855 by reference for energy storage systems. Florida does not use the IFC at all. It enforces its own Florida Fire Prevention Code, currently the 8th edition, which is built on NFPA 1 and NFPA 101 rather than the IFC and is administered by the State Fire Marshal. Arizona has no statewide fire code, so each city or county adopts its own, most commonly a recent edition of the IFC.
The local authority having jurisdiction, or AHJ, is the final decision maker. The AHJ can require more than the code minimum, as happened in Goodyear, Arizona, where after a thermal runaway incident at a Microsoft data campus the fire marshal required the battery room to be relocated to a position more accessible to first responders in the next AI data center built. NFPA Journal
What do these rules mean for AI data center developers, operators, and lenders?
Compliance is expensive, and the cost grows with the amount of lithium ion stored energy. A single large scale fire test under UL 9540A can cost $40,000 to $100,000 or more per system. UL 9540A testing cost guide Adding explosion control systems, enhanced ventilation, fire resistive barriers, and water storage all increase the construction budget.
The insurance market has noticed. FM Global recommendations often become deal terms. Lease agreements and power offtake contracts increasingly include conditions requiring the operator to comply with NFPA 855, to maintain specific fire protection arrangements, and to warrant that the battery installation meets local fire code. Law firm analysis
A growing number of operators are exploring battery chemistries that avoid thermal runaway risk entirely. Nickel zinc batteries, for example, are not subject to the 600 kWh per enclosure limit and do not require the same explosion control measures. ZincFive alone has surpassed 2 gigawatts of nickel zinc power delivered or contracted globally for data centers. ZincFive Another option is organic flow batteries, like the system Prometheus Hyperscale plans to install in Wyoming by 2027, which eliminates lithium entirely. Industry news
For lenders, the state of the battery safety rules affects both the cost and the risk profile of the asset. Lenders are asking for proof of UL 9540 listing, confirmation that the local fire marshal has approved the installation, and evidence that the operator has an emergency response plan that meets the NFPA 855 requirements for immediate evacuation and firefighter coordination.
Key takeaways
- NFPA 855 applies to lithium ion battery energy storage systems over 20 kWh, limits them to 600 kWh per fire enclosure, and the 2026 edition mandates a hazard mitigation analysis and explosion control system for most installations.
- Every stationary energy storage system must be UL 9540 listed, and the IFC or NFPA 1 requires construction and operational permits.
- Clean agent fire suppression alone will not stop a lithium ion battery fire. Water sprinklers or water mist systems are necessary to cool the cells.
- FM Global Data Sheets 5-32 and 5-33 set insurer driven fire protection requirements that often exceed the code minimums, and lenders and carriers treat them as de facto standards.
- Shipping lithium ion batteries to and from the AI data center triggers DOT packaging, marking, and state of charge limits, with no passenger aircraft allowed for UN3480.
- End of life batteries are likely hazardous waste. The universal waste program offers a streamlined disposal process, but damaged batteries must go the full hazardous waste route. The EPA is expected to issue lithium specific universal waste rules.
- Store more than 10,000 pounds of lithium ion batteries on site, and you must file a Tier II inventory report under EPCRA, and OSHA requires safety data sheets and labels because lithium-ion batteries are not articles.
- Local fire code adoption varies widely. Check which edition of the IFC or NFPA 1 the local AHJ enforces, because it determines which version of NFPA 855 applies.
Frequently asked questions
Q:At what capacity does NFPA 855 start to apply to a lithium-ion battery system in an AI data center?
A:At 20 kWh of stored energy for lithium-ion chemistries. Below that threshold the standard does not apply. NFPA 855 Table 1.3
Q:What is the maximum amount of lithium-ion battery storage allowed in one room under NFPA 855?
A:600 kWh per fire enclosure area. That ceiling drives the need for multiple battery rooms in large AI data centers. NFPA 855 (2023)
Q:Is a UL 9540 listing mandatory for a data center energy storage system?
A:Yes. Both the IFC and NFPA 855 require the energy storage system to be UL 9540 listed. IFC § 1207.3.1, NFPA 855 § 15.2
Q:Can a clean agent fire suppression system protect a lithium-ion battery room?
A:Not on its own. Clean agents cool nothing and cannot stop a thermal runaway reaction inside the cells. A water-based system is highly recommended. News analysis
Q:What does the 2026 NFPA 855 require that earlier editions did not?
A:A hazard mitigation analysis is now required for most installations, not just those above a stored energy threshold. Explosion control must meet NFPA 69 or a performance-based alternative validated by installation-level fire and explosion testing, and deflagration venting alone is no longer accepted as the primary strategy. NFPA 855 (2026)
Q:Do lithium-ion batteries need to be managed as hazardous waste when they are removed from service?
A:In most cases, yes. The EPA expects them to exhibit ignitability and reactivity, so they should be managed as universal waste or, if the damage breaches a cell casing, as fully regulated hazardous waste. EPA FAQ
Q:What federal transportation limit applies to lithium-ion batteries on cargo aircraft?
A:The batteries must be at 30 percent state of charge or less, and the net battery weight per package is limited to 35 kg. PHMSA Guide, PHMSA Interpretation 22-0110
Q:When does an AI data center operator need to file a Tier II chemical inventory report for lithium-ion batteries?
A:The federal threshold is 10,000 pounds of hazardous chemicals present at any one time. Some states and localities have lower thresholds. 40 CFR 370.10, EPA Hazardous Chemical Inventory Reporting, EPA Tier II Instructions
Q:Which edition of NFPA 855 applies to my AI data center project?
A:It depends on the state and local adoption of the IFC or NFPA 1. For example, Virginia uses the 2021 IFC, and Texas enforces the 2020 NFPA 855 under the State Fire Marshal. You must confirm the local code edition with the authority having jurisdiction.
Q:Are there battery chemistries that avoid these strict fire code requirements?
A:Nickel-zinc and lead-acid batteries have a higher NFPA 855 threshold (70 kWh) and no 600 kWh per room capacity cap. Nickel-zinc is inherently resistant to thermal runaway. Some operators are also turning to organic flow batteries. DCD, Industry news, NFPA 855 analysis
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Junde Liu, JD, LL.M. (Taxation) candidate at UF Law. Originally published on Compute Law Blog. This article is general information and does not constitute legal advice. Reading it does not create an attorney client relationship. The reader should not act on the basis of any content here without first consulting a licensed attorney in the relevant state. Last reviewed for accuracy May 23, 2026.