The latest version of BS ISO 3941:2026 has been published with a revision to include a new fire classification for lithium-ion (Li-ion) battery fires
BS ISO 3941:2026 Classification of fires categorises the different kinds of fires defined by the nature of the material undergoing combustion, with the latest revision introducing Class L as a dedicated fire classification involving Li-ion cells and batteries where no metallic lithium is present.
The new classification was deemed necessary due to the specific behaviours shown by Li-ion batteries in a fire incident. These include:
- higher energy density, leading to faster heat release and rapid fire growth
- thermal runaway, where failure can propagate from cell-to-cell
- toxic and flammable gas release during venting
- potential explosion risk from constrained vented gas build-up
- limited access due to battery construction
- projectile risk from expelled cells and burning electrolyte
- stranded electrical energy leading to potential delayed re-ignition.
