Lithium-ion battery fire risk in buildings: a proportionate response

Lithium-ion battery technology powers the devices that most of us carry and the vehicles that growing numbers of people own. Smartphones, laptops, electric bicycles, electric scooters (e-scooters), and electric cars all use lithium-ion cells in various configurations. The technology is mature, widely used, and, when properly manufactured and managed, generally safe.

However, lithium-ion batteries can fail, and when they do, the consequences can be serious. The failure mode known as thermal runaway — a self-sustaining, exothermic reaction within the cell — can produce intense heat, fire, and toxic gases that are difficult to suppress with conventional means. Incidents involving e-bikes and e-scooters in particular have received significant attention in recent years, and fire and rescue services have reported increases in battery-related fires.

This article is for duty holders — responsible persons, building managers, facilities managers — who need to understand the risk in their buildings and put proportionate arrangements in place. The starting point is a clear-eyed look at what the risk actually is, rather than either dismissing it or overstating it.

Understanding the risk

The risk from lithium-ion batteries in a building setting varies significantly with the type and size of the battery, how it is used and stored, and whether it is in good condition and has been charged with the correct equipment. The large-format batteries in modern electric cars are engineered and protected to a different standard from the smaller, sometimes poorly manufactured cells in cheap e-bikes and e-scooters. Both warrant consideration in a fire risk assessment, but they are different risks.

Thermal runaway can be triggered by physical damage to a cell, by overcharging, by charging with incompatible or faulty equipment, or by cell defects. Once initiated, it can spread rapidly through a battery pack, producing heat and toxic gases at a rate that can overwhelm a sprinkler system and that the water from a conventional fire hose may not easily extinguish. The risk is therefore highest at the point of charging — particularly overnight charging of large-format batteries — and where batteries have been damaged.

The risk does not, however, justify treating all lithium-ion batteries in all buildings as an acute hazard requiring immediate action. The great majority of charged devices in most buildings — including mobile phones, laptops, and power tools — present a low and manageable risk when used and stored in accordance with manufacturers' guidance. The focus of risk management should be on the higher-risk scenarios: large-format batteries, high-intensity charging, damaged or modified batteries, and the use of incompatible charging equipment.

The fire risk assessment is the right tool

Managing lithium-ion battery risk in a building is a fire risk assessment matter. The Regulatory Reform (Fire Safety) Order 2005 (RRFSO) requires the responsible person to carry out a suitable and sufficient fire risk assessment for the premises and to implement the findings. Battery-related risks should be included in the assessment where they are present and material to the overall risk picture.

For most commercial premises — an office, a school classroom, a hotel — the battery risk is primarily from small devices and is low compared with the building's other fire risks. The assessment should note this and record that the risk is managed by standard good practice (staff awareness, no overnight charging of personal devices at unattended workstations, no use of unapproved chargers on company equipment). No special measures are needed in most cases.

The picture is different in residential buildings where e-bike or e-scooter ownership is common, in education settings with electric vehicle charging on site, and in workplaces where battery-powered tools or equipment is central to the operation. In those cases, the assessment needs to give greater attention to storage and charging arrangements and the controls in place.

Proportionate management measures

For buildings where large-format batteries are regularly charged, the most effective risk management measures are practical and do not require significant capital expenditure. They include: designating specific locations for charging that are away from sleeping areas and escape routes; not leaving batteries on charge unattended for extended periods, particularly overnight; using only charging equipment that is compatible with the battery and complies with the relevant electrical safety standards; inspecting batteries regularly for damage and withdrawing damaged batteries from use; and ensuring that those responsible for charging understand the risks and the procedures.

For residential buildings, the challenge is that the responsible person's control over residents' behaviour within their own homes is limited. The practical approach is to address the communal areas and shared spaces — establishing clear rules about e-bike and e-scooter storage and charging in communal areas, enforcing a prohibition on charging in stairwells and lobbies, and providing guidance to residents about safe home charging practice.

In settings where e-bike or e-scooter charging facilities are being installed or are already in place, the design and location of those facilities should be considered as part of the fire risk assessment. Locating charging facilities in detached or separated structures, or in areas with good passive fire separation from sleeping or occupied areas, significantly reduces the consequences of a battery fire.

Detection and suppression

Smoke detection is the primary means of early warning for battery fires, and it is already required in the settings where lithium-ion battery risk is most acute. Ensuring that automatic fire detection in communal areas and, where required, within individual dwellings is properly installed, maintained, and tested is a prerequisite before addressing more specific battery-risk measures.

Some building managers have asked whether automatic suppression systems (sprinklers) adequately address lithium-ion battery fires. Sprinklers will limit the spread of a fire and protect the building, but they may not extinguish a lithium-ion fire at source — the thermal runaway reaction within a cell can continue even when the external flames are suppressed. The practical implication is that the fire and rescue service will typically need to cool the battery for an extended period. This does not mean sprinklers are unhelpful — they significantly reduce the risk to the building and its occupants. But sprinkler protection should not be the primary risk management strategy for a known battery-charging risk in a vulnerable location.

What good looks like for a duty holder

For most duty holders, the objective is straightforward: a fire risk assessment that has genuinely considered the lithium-ion battery risk in the building, a clear set of practical management measures that address the highest-risk scenarios, and residents or staff who understand the basic safe-use guidance. None of this requires expensive specialist equipment or a complex management programme. It requires clear thinking about where the risk actually sits and consistent application of practical controls.

Apex's fire risk assessment service considers lithium-ion battery risk as part of the overall fire risk picture for any building where it is material. The assessment will identify the relevant risk scenarios, assess the adequacy of existing arrangements, and recommend measures proportionate to the actual risk — not a standardised set of requirements applied regardless of context.