A new edition of the international standard ISO 3941:2026 has been published, introducing a new fire classification: Class "L", which covers lithium-ion battery fires.
This new class was deemed necessary due to the specific behaviors exhibited by Li-ion batteries during fire incidents. These include:
- Higher energy density, leading to faster heat release and rapid fire spread;
- Thermal runaway, where a failure can propagate from one cell to another;
- Release of toxic and flammable gases during the "venting" phase;
- Potential explosion risk due to gas accumulation in confined spaces;
- Difficult access caused by the battery's design;
- Projectile risk related to the ejection of cells and ignited electrolyte;
- Stored electrical energy which can lead to delayed reignition.
The new Class L will require particular attention to be paid to the aforementioned risks when designing detection and suppression strategies and systems. It also necessitates new approaches for managing reignition risks and re-evaluating emergency response plans.
However, within the European Union, the authoritative standard for fire classes is not ISO 3941, but rather the European standard EN 2. As the content of these two standards is harmonized, the update of EN 2 will be based on the revised ISO standard and will also introduce the new Class L.
Find more information in our ANPI Magazine No. 43, June 2026.
