Allstate Sprinkler Releases Analysis Linking ISO Class L Fire Rating to NYC 1 kWh Storage Threshold

Bronx, NY, USA, September 8th, 2026, FinanceWire

Allstate Sprinkler today published an operational analysis evaluating how the ISO 3941:2026 Class L fire designation compliments the 1 kWh energy storage system (ESS) threshold enacted by New York. This analysis examines the overlap between international battery hazard standards and the local regulatory framework. Allstate Sprinkler’s analysis concluded that the ISO standards help officially identify and articulate some hazard profiles that the New York City municipal code has already incorporated and enforced through a regulatory approach to ESS and battery-powered devices.

ISO Class L New York City’s 1 kWh ESS Threshold

Allstate Sprinkler reports that in 2026 the International Organization for Standardization released the third iteration of ISO 3941, replacing the 2007 version and included the Class L designation for lithium-ion cells and batteries that do not contain lithium metal components. The ISO standard identifies Class L as a major technical revision to the standard driven by the need to incorporate risk factors specific to lithium-ion technology. 

These risks include higher energy density, rapid fire propagation, and potential for toxic/flammable venting gasses, cascading thermal runaway, stranded electrical energy upon suppression, and re-ignition. The standard differentiates Class L from Class D fires involving combustible metals, underscoring the unique risks presented by lithium-ion systems.

While ISO standards are voluntary guidelines, the City of New York has long had regulations addressing fire hazards in energy storing facilities. Under the City’s adoption of NFPA 855, any lithium-ion energy storage system above the 1 kWh threshold will trigger regulatory requirements. In contrast, the threshold for lead acid batteries remain at 70 kWh. The seventy-fold increase signals the proactive approach taken at the city level.

Addressing FDNY Data and Suppression Limitations

Allstate Sprinkler’s findings are consistent with data within New York City. During 2025, there were 277 fires involving lithium-ion batteries in New York City, up from 268 in the previous year and accounting for six fatalities as of late 2024, down from 18 in 2023. A look by the FDNY into the 2023 incidents reveals that more than half of lithium-ion battery fires did not involve active charging, instead causes included damage, battery age, storage density, or non-certified charging equipment.

These represent an ongoing risk of cascading thermal runaway that water-based sprinklers cannot mitigate. New York State law, from January 5 2026, requires statewide warning labels for charging cables on new lithium-ion powered micromobility products.

Allstate Sprinkler notes that existing fire sprinkler inspections, under NFPA 25, do not qualify as an assessment of the hazards in lithium-ion battery energy storage systems. Standard NFPA 25 maintenance inspections evaluate existing water sprinkler systems based on system performance against the original design, but fail to address any issues or characteristics of the batteries themselves, or their installation relative to the threshold.

The analysis was based on specifications for the ISO 3941:2026 standards, New York City Fire Department and Department of Buildings code requirements referencing NFPA 855, New York State Department of State legislation, and FDNY fire incident data.

Frequently Asked Questions

ISO 3941:2026 Class L

Allstate Sprinkler describes the ISO 3941:2026 Class L designation as the fire classification for all lithium-ion cells and batteries without lithium metal components. Class L isolated the specific hazards of electrochemical systems including thermal runaway, gas venting, and re-ignition from those presented by combustible metals.

New York City ESS Thresholds

Allstate Sprinkler notes that under New York City’s regulations based on NFPA 855, lithium-ion ESS with over 1 kWh capacity will face stricter requirements including third-party certification and FDNY approval. These requirements are in contrast to the 70 kWh threshold for traditional lead-acid batteries.

FDNY Lithium Ion Battery Fire Data

Allstate Sprinkler’s review of FDNY data indicates that nearly 60% of lithium-ion battery fires occurred without active charging, pointing to factors such as damage, aging, storage conditions, and uncertified charging equipment.

About Allstate Sprinkler

Allstate Sprinkler is a Licensed Master Fire Suppression Contractor providing inspection, testing, repair, and emergency suppression services across New York City, Westchester, Long Island, and Northern New Jersey since 1972.

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