The moment lithium-ion stopped being “just another fire”.

There has been a quiet but significant shift in the fire safety landscape.

The latest revision of ISO 3941 has introduced a new classification: Class L for lithium-ion battery fires. At first glance, this may appear to be a technical housekeeping exercise. It is not. It is a recognition that something fundamental has changed.

For decades, we have worked within a stable framework of fire classes. Solids, liquids, gases, metals, cooking oils. Each with broadly understood behaviours and corresponding extinguishing strategies. Lithium-ion fires have, until now, been awkwardly accommodated within that framework, often treated as a variation of electrical or Class A fires.

That position is no longer tenable.

Lithium-ion battery fires are not defined solely by the materials involved, but by the mechanism driving them. Thermal runaway, self-sustaining reactions, rapid energy release, and a propensity for re-ignition fundamentally distinguish these events from conventional fires. The introduction of Class L is, in effect, an admission that the existing categories were not sufficient.

This matters, because classification underpins everything else.

It informs how we design, how we assess risk, how we select protection measures, and how we train people to respond. If the classification changes, the assumptions that sit behind those decisions must also be revisited.

And yet, much of current practice has not caught up.

There remains a tendency to treat lithium-ion fires as manageable within existing paradigms. This is most visible in the growing number of products marketed as capable of addressing “all fires”, including lithium-ion battery incidents. These claims may be well intentioned, and in some cases supported by testing, but they sit uneasily alongside the recognition that this is now a distinct class of fire with its own behaviour and hazards.

There is a more uncomfortable question here.

If lithium-ion fires are fundamentally different, what does that mean for first response? In particular, what does it mean for expectations placed on staff, occupants, or other non-specialists to intervene using portable extinguishers?

In many cases, the safer and more appropriate response may not be intervention at all. Containment, evacuation, and allowing the event to be managed by appropriately equipped fire and rescue services may represent a more realistic strategy, particularly where thermal runaway is established.

This is not to suggest that extinguishers have no role. They may still be entirely appropriate for incipient fires, for surrounding materials, or for preventing fire spread in the early stages. But the assumption that a single extinguisher can reliably and safely address a lithium-ion battery fire in all circumstances deserves careful scrutiny.

The introduction of Class L does not, in itself, provide all the answers. It does, however, provide clarity on one point.

Lithium-ion fires are no longer “just another fire”.

The industry now needs to respond accordingly.

This commentary is provided as a general professional reflection on emerging issues in fire safety. It is not project-specific advice and should not be relied upon as a substitute for a detailed, site-specific fire risk assessment or engineering appraisal.