A New Fire Classification Standard Has Been Published – Including a New Fire Class
This is the first significant structural update to fire classification in many years, reflecting the increased presence of lithium-ion battery risks in modern premises.
The introduction of Class L clarifies how these risks should be categorised within fire risk assessments. Although extinguisher fire ratings under BS EN 3 remain unchanged, the update strengthens the expectation that lithium-ion battery hazards are properly identified and addressed where present.
What Does BS ISO 3941:2026 Do?
BS ISO 3941:2026 sets out the internationally aligned fire classification framework adopted in the UK. It introduces Class L alongside the existing fire classes:
-
Class A – Solid combustibles (wood, paper, textiles, plastics)
-
Class B – Flammable liquids (petrol, solvents, paints)
-
Class C – Flammable gases (propane, butane, methane)
-
Class D – Combustible metals (magnesium, lithium metal, sodium)
-
Class F – Cooking oils and fats (deep fat fryers)
-
Class L – Fires involving lithium-ion cells and battery packs (where no metallic lithium is present)
Importantly, the introduction of Class L does not change existing extinguisher fire ratings under BS EN 3.
Why Class L Has Been Introduced
The introduction of Class L reflects the significant growth in lithium-ion battery use across modern premises, including:
-
Electric vehicles and e-bikes
-
Energy storage systems
-
Portable tools and equipment
-
Consumer electronics
Lithium-ion battery fires behave differently from traditional combustible materials or flammable liquids. In particular, thermal runaway can lead to rapid heat release, re-ignition and complex fire development.
Previously, lithium-ion battery fires were typically considered under existing fire classes depending on the materials involved. The introduction of Class L provides clearer categorisation for risk assessment and fire safety planning purposes.
It does not invalidate existing classifications, but clarifies how lithium-ion battery hazards should be described where present.
“Where lithium-ion battery risks are present, fire risk assessments should be reviewed to ensure hazards are clearly identified and appropriately categorised in line with BS ISO 3941:2026. This supports compliance with the Regulatory Reform (Fire Safety) Order 2005.”
Important Clarification on Electrical Fires
-
Electrical fires are not a separate fire class under UK fire classification standards.
-
Electricity is an ignition source. Once isolated, the fire is classified according to the burning material involved.
-
The term “Class E” is no longer recognised under current UK fire classification standards and should not be used in new fire safety documentation.
-
Class L should not be confused with “electrical fires”; it specifically relates to lithium-ion battery cells and battery packs.
-
Extinguishers suitable for use on live electrical equipment are selected based on their tested suitability for electrical risk, not because “electrical fire” is a separate class.
How This Links to BS 5306 (Fire Extinguishers)
BS ISO 3941 defines how fires are classified.
BS 5306 then provides guidance on:
-
What extinguisher type is appropriate
-
How many are required
-
Where they should be positioned
-
How they should be maintained
In simple terms:
-
BS ISO 3941 defines the fire classification framework.
-
BS 5306 provides guidance on the provision of extinguishers.
BS 5306-8 specifically covers the selection and positioning of portable fire extinguishers and currently provides guidance for Classes A, B, C, D, and F. When Class L risks are identified in your fire risk assessment, you should consider whether your standard extinguisher provision remains adequate or whether specialist equipment, such as lithium-ion fire blankets or AVD (Aqueous Vermiculite Dispersion) extinguishers, should be provided in addition to your existing extinguishers. Class L does not replace your current requirements; it supplements them where lithium-ion battery hazards are present.
Accurate identification of fire risks helps ensure that extinguisher provision is appropriate for the hazards present.
The introduction of Class L provides clearer categorisation of lithium-ion battery risks, which should be considered within fire risk assessments where relevant.
What This Means for Fire Safety Order Compliance
Under the Regulatory Reform (Fire Safety) Order 2005, Responsible Persons must:
-
Carry out a suitable and sufficient fire risk assessment (Article 9)
-
Provide appropriate fire-fighting equipment (Article 13)
-
Maintain fire safety measures (Article 17)
Correct fire classification in line with BS ISO 3941 supports:
✔ Accurate hazard identification ✔ Appropriate extinguisher selection ✔ Evidence of due diligence ✔ Alignment with recognised best practice
Where lithium-ion battery hazards are present, they should be clearly identified within the fire risk assessment. Failure to adequately assess such risks could result in an incomplete assessment under Article 9 of the Regulatory Reform (Fire Safety) Order 2005.
While British Standards are not law, enforcing authorities and courts may refer to them when considering whether a Responsible Person has acted reasonably and proportionately.
What You Should Do Now
We recommend that you:
-
Review your fire risk assessment templates
-
Ensure lithium-ion battery hazards are considered where applicable
-
Remove outdated references to “Class E” electrical fires in new documentation
-
Check that extinguisher schedules and fire risk assessments accurately reflect the hazards present
-
Confirm your fire safety contractor is working to the current standards
-
Update staff training materials where relevant
If your documentation still references older terminology, consider updating it to reflect current classification standards.
Discuss Lithium-Ion Battery Risks in Your Premises SPEAK TO US
Need Help Updating Your Fire Documentation?
We are currently supporting clients in reviewing their fire risk assessments and documentation to ensure lithium-ion battery hazards are clearly identified where relevant and aligned with current classification standards, including BS ISO 3941:2026.
If you would like your fire risk assessment reviewed or updated, contact us to discuss your premises and risk profile.
✅ Stay compliant with the latest fire safety laws ✅ Get exclusive security advice from industry experts ✅ Learn how to protect your people, property, and assets
