The rapid growth of lithium-ion batteries across industry — from electric forklift fleets to large-scale energy storage systems — has created a fire and containment risk that conventional spill control equipment is wholly inadequate to address. Thermal runaway events in lithium batteries are unlike any other industrial fire. Understanding the chemistry, the containment requirements, and the correct emergency response is no longer optional for UK facilities managing battery technology at scale.
What Is Thermal Runaway?
Thermal runaway is an exothermic chain reaction within a lithium-ion cell in which rising temperature causes further chemical decomposition, which generates more heat, creating a self-sustaining and accelerating reaction. It can be triggered by:
- Physical damage or mechanical impact (crash, crush, penetration)
- Overcharging or over-discharging
- Manufacturing defects (internal short circuit)
- External heat exposure
Once initiated, thermal runaway cannot be stopped by removing the energy source. The battery itself is the fuel.
Why Thermal Runaway Is Different
During thermal runaway, a lithium battery releases:
- Extreme heat: Cell temperatures can exceed 800°C — far beyond the capability of standard spill containment plastics (HDPE degrades at ~120°C, polypropylene at ~160°C)
- Toxic gases: Hydrogen fluoride (HF), carbon monoxide (CO), hydrogen cyanide (HCN), and volatile organic compounds — all acutely toxic
- Electrolyte ejection: The liquid electrolyte (typically lithium hexafluorophosphate, LiPF6, in organic solvent) is ejected as a flammable, corrosive aerosol and liquid spill
- Projectile risk: Venting cells can eject material at high velocity
Standard spill pallets, drip trays, and even bunded COSHH stores are not designed for these conditions. A plastic spill pallet placed under a lithium battery pack will melt and fail long before the fire is extinguished.
Electrolyte Containment: Material Selection
When electrolyte is spilled without thermal runaway (e.g., from a damaged cell), the correct containment material is high-density polyethylene (HDPE). HDPE is chemically resistant to LiPF6-based electrolytes and the organic solvents (ethylene carbonate, dimethyl carbonate) they contain.
Do not use galvanised steel for electrolyte containment — the zinc coating reacts with the fluoride compounds in electrolytes, accelerating corrosion and potentially generating hazardous by-products.
Correct Storage Requirements for Lithium Batteries
The Environment Agency and HSE guidance recommends that lithium battery storage at scale should use one of the following approaches:
- Separate fire-rated structure: A dedicated building or container with minimum 60-minute fire resistance, fire suppression systems, and ventilation to manage off-gassing
- Certified lithium battery storage cabinet: Purpose-built units with fire-rated construction, gas filtration, and internal suppression — compliant with BS EN 62619 (safety requirements for stationary lithium battery systems)
BS EN 62619:2022 sets the safety standard for stationary lithium battery installations, covering electrical safety, thermal management, and containment. It applies to battery energy storage systems (BESS) and is increasingly referenced in planning conditions for grid-scale battery installations.
Comparison: Lithium Battery Fire vs Traditional Chemical Fire
| Property | Lithium Battery Fire (Thermal Runaway) | Traditional Flammable Liquid Fire |
|---|---|---|
| Peak Temperature | 800°C – 1,000°C+ | 300°C – 600°C (varies by fuel) |
| Self-Sustaining? | Yes — battery is both fuel and oxidiser | No — remove fuel or oxygen to extinguish |
| Toxic Gas Release | HF, CO, HCN, VOCs — acutely toxic | CO, CO2, soot — varies by fuel |
| Correct Extinguishing Agent | Water (large volumes, sustained cooling) | Foam, CO2, dry powder (water can spread) |
| Containment Material | Fire-rated structure; HDPE for electrolyte spill | Steel bund, HDPE or PP spill pallet |
| Re-ignition Risk | Very high — cells can re-ignite hours later | Low once fuel removed |
| Evacuation Zone | Minimum 25m — toxic gas plume risk | Standard fire response perimeter |
| Regulatory Standard | BS EN 62619, EA BESS guidance 2023 | DSEAR 2002, BS EN 14470-1 |
Emergency Response: Water Is Correct for Lithium Fires
This is a critical point that surprises many safety managers: water is the correct extinguishing agent for lithium-ion battery fires. Unlike lithium metal fires (Class D, where water reacts violently), lithium-ion chemistry does not react dangerously with water. Large volumes of water are required to cool cells and prevent re-ignition. CO2 and dry powder extinguishers are ineffective because they cannot penetrate the cell structure and reduce temperature.
Responders should wear full SCBA (self-contained breathing apparatus) due to the toxic gas hazard, and the area must be ventilated before re-entry even after apparent extinguishment.
Key Actions for UK Facilities
If your site stores, charges, or operates lithium battery equipment:
- Conduct a DSEAR/COSHH assessment specifically for battery off-gassing zones
- Replace standard spill pallets with fire-rated lithium battery containment units
- Ensure your PIRP identifies lithium battery incidents as a separate scenario
- Train staff on water-based response and the re-ignition risk
- Check your fire suppression system is rated for battery fires
Need expert advice? Call 01744 520 110