International Update: ISO 3941:2026 Introduces Class L for Lithium-Ion Battery Fires
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Time to read 2 min
In January 2026, the International Organization for Standardization (ISO) published ISO 3941:2026 – Classification of Fires (3rd Edition).
Key Update: Introduction of Class L
ISO 3941:2026 introduces a new fire classification, Class L, specifically for lithium-ion battery fires. This formally acknowledges that lithium-ion battery fires present unique characteristics, including high energy release, sustained thermal runaway, and re-ignition risk, which clearly distinguish them from traditional fire classes.
ISO 3941:2026 defines classes of fires according to the nature of the material undergoing combustion. In consequence, it does not define a particular class of fire involving an electrical risk.
In this new standard, Class L (Lithium-ion battery) fires are defined as electrochemical fires, not electrical fires (Class E).
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Feature |
Electrical Fire (Live Equipment) |
Electrochemical Fire (Battery/Cell) |
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Primary Cause |
Overloaded circuits, faulty wiring, and damaged equipment. |
Thermal runaway, physical damage, overcharging, internal shorts. |
|
Burning Material |
Cable insulation, surrounding insulation, plastic casing. |
Electrolytes, cathode/anode materials (e.g., Lithium). |
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Fuel Source |
External (surrounding materials). |
Internal (the battery itself). |
|
Oxygen Need |
Needs oxygen from the air. |
Generates oxygen internally (self-sustaining). |
|
Behavior |
Extinguishes when power is cut (unless it spreads to Class A). |
Very difficult to stop; can re-ignite after being put out. |
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Extinguisher |
CO2, Dry Powder (Class E). |
Large amounts of water (cooling), Specialised agents. |
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Key Danger |
Electrocution, fast-spreading. |
Toxic gases (HF), rapid explosion-like energy release. |
Read more here ISO 3941:2026
Why This Matters
Class L applies specifically to fires involving lithium-ion batteries. Metallic lithium remains classified under Class D, and is not included in Class L. Lithium-ion battery fires are now formally recognised as distinct from traditional Classes A–F.
This international recognition confirms what testing, incident data, and real-world experience have consistently shown: lithium-ion battery fires are not effectively addressed using conventional electrical (Class E) fire assumptions or traditional extinguishing approaches alone.
Relationship to NTA 8133 and Emerging Standards
ISO 3941:2026 establishes the formal fire classification framework, while KIWA NTA 8133 continues to serve as the recognised performance-based test method for assessing whether a fire extinguisher can manage the specific hazards presented by a lithium-ion battery fire.
· These two standards are complementary and serve different purposes:
· ISO 3941:2026 defines what a lithium-ion battery fire is (Class L).
NTA 8133 provides the rigorous testing methodology used to verify how extinguishers perform against these fires.
This approach is now being actively incorporated into international standards development, including the forthcoming EN 3-11, which is expected to further formalise lithium-ion fire performance requirements.
Reinforcing Our Previous Position
This international development strongly supports the position outlined in our earlier TAN-09 communication:
· Lithium-ion battery fires are fundamentally different from traditional electrical fires.
· Treating lithium-ion battery fires as Class E is no longer aligned with emerging international standards and evidence.
· Effective lithium-ion battery fire protection relies on cooling and thermal management as the primary control mechanism, not electrical isolation alone.
Li-ion Fire Solutions will continue to monitor global standards developments closely and align our guidance, products, and supporting information accordingly. We support the continued progression toward clear, lithium-ion-specific standards that improve safety outcomes, provide certainty for industry, and reflect the realities of lithium-ion battery fire behaviour.
For customers seeking a more detailed explanation, including supporting evidence, testing references, and information gathered over several years, further information is available at: www.lithium-ionfireprotection.com.au
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