Class L Battery Fires - What Lithium-Ion Fires Are Finally Being Recognized For
A new chapter has entered the fire safety codes. One that reshapes how we classify risk, design protection, and understand combustion itself. With the release of ISO 3941:2026, lithium-ion battery fires are no longer folded into the margins of Class A or B. They now stand alone, under a newly designated banner: Class L.
The new classification acknowledges what operators, engineers, and insurers have long witnessed on the ground: lithium-ion fires behave differently. They ignite invisibly, escalate chemically, and persist long after flames subside. The risk is not simply thermal, it is electrochemical, architectural, and operational all at once.
Across sectors, this classification lands at a time of convergence. Energy storage is booming, power grids are decentralising, and electrification is reaching every corner of the built environment. From residential buildings to remote substations, lithium-ion batteries have become the connective tissue of modern energy resilience. But as their footprint grows, so too does the complexity of protecting it.
In the UK, the Fire Protection Association (FPA) and BSI have underscored the unique hazard profile of these batteries: thermal runaway, toxic gas release, cell-to-cell propagation, reignition risk, and structural access barriers. Each characteristic disrupts traditional suppression logic. Water is often inadequate. Extinguishers are outpaced. Reignition is common. The conclusion is stark: detection and suppression strategies must evolve.
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
At DSPA Sustainable Fire Suppression, we welcome this evolution. It validates what our engineers have built into our aerosol fire suppression systems for years: a certified hold time of at least 30 minutes, engineered to control gas-phase combustion, suppress ignition risks, and crucially, prevent fire propagation across battery cells during thermal runaway events. In environments such as BESS containers, where reignition is a persistent threat, this extended hold time is unmatched in the market. It ensures complete fire suppression, maintains atmospheric stability, and creates a safer window for responders and infrastructure alike.
While Class L currently lacks dedicated testing standards for fixed systems, DSPA aerosol generators are dimensioned for enclosed fire scenarios with the highest thermal load, consistent with the density and severity associated with critical risk environments such as battery storage systems and thermal runaway events. Until Class L methodologies are formally defined, this remains the most robust and technically sound benchmark available in the absence of a dedicated fire extinguishing test for the specific solution.
In addition to ISO 3941, protocols such as KIWA’s K21045-SCP05 provide further technical validation. This certification program was developed to test fire protection systems in lithium-ion battery storage environments under defined configurations. It evaluates not only the fire suppression performance, but also the integration of detection, system design, compartment structure, and post-activation safety. Although no universal fire class exists yet for lithium-ion cells, programs like SCP05 represent a practical and credible benchmark for verifying protection concepts in real-world applications.
More than a product response, this is a call for systemic readiness. Fire risk assessments must now account for lithium-ion technologies as primary hazards. Standards are catching up. Insurance is watching closely. And forward-leaning operators are already retrofitting.
To those navigating this landscape, we offer not just equipment, but insight. We are engaging with partners to help them interpret this new standard, adapt their infrastructure, and future-proof their fire protection.
To learn more about how DSPA Aerosol protects lithium-ion battery storage systems, visit:
