Lithium-ion batteries, lithium-polymer cells, and related energy storage devices have become an integral part of modern buildings: They are found in electric vehicles, pedelecs, power tools, emergency power systems, and countless small appliances. But storing batteries means storing concentrated chemical energy in a component that can react uncontrollably under certain conditions. Fire safety in battery storage is therefore not a minor bureaucratic issue, but a serious design and organizational challenge that affects architects, planners, operators, and users alike.
- Why lithium-based batteries pose a particular fire risk and how so-called thermal runaway occurs
- Which storage quantities, storage types, and usage profiles require which protective measures
- What building code and regulatory requirements apply to battery storage
- How storage rooms, storage boxes, and charging infrastructure should be designed and constructed
- What role fire detection systems, suppression systems, and firefighting water play in battery fires
- How fire safety requirements vary depending on the building type and use
- What common mistakes to avoid during planning and operation
- How this topic fits into a building’s overall fire protection planning
The specific fire risk posed by lithium batteries: thermal runaway and its consequences
To understand the fire safety requirements for storing batteries, one must first grasp what happens inside a lithium cell when it reacts uncontrollably. The key term here is “thermal runaway.” This refers to a self-sustaining chain reaction within the cell: If the temperature rises above a critical threshold, the cell releases additional heat through exothermic decomposition reactions, which further increases the temperature, which in turn triggers further reactions. Once this process has begun, it can no longer be stopped without external intervention.
The causes of thermal runaway are varied. Mechanical damage to the cell, deep discharge below the permissible minimum voltage, overcharging, external heat sources, manufacturing defects, or signs of aging can trigger the process. What makes this particularly treacherous is that a damaged or improperly charged cell can develop thermal runaway with a significant time delay: hours or even days after the triggering event, the cell may suddenly begin to smoke and catch fire. For warehouse planning, this means that a battery that appears undamaged on the outside may still pose a latent risk.
The fire characteristics of lithium batteries differ fundamentally from those of conventional fires. During thermal runaway, lithium cells release flammable and toxic gases, including hydrogen, carbon monoxide, and hydrogen fluoride. These gases can accumulate in enclosed spaces and create an explosive atmosphere before a visible flame develops. In addition, a fire in a single cell can spread to neighboring cells—an effect known as cell-to-cell propagation. A battery pack consisting of hundreds of individual cells can therefore cause a fire that far exceeds a comparable conventional fire in terms of intensity and duration.
For firefighters, a lithium-ion battery fire poses a particular challenge. Water cools the cells and prevents thermal runaway from spreading to neighboring cells, but it does not extinguish the reaction within a cell that is already affected. Large amounts of water are required, and the firefighting operation can last for hours. Extinguished batteries can reignite after hours or days, which is why they must be stored underwater or secured in special containers after a fire. These characteristics make it clear why preventive fire protection is so much more important when storing batteries than with conventional fire loads.
Regulatory and Building Code Foundations: What Are the Fire Safety Requirements for Storing Batteries?
The regulatory landscape for storing batteries from a fire safety perspective is still evolving in Germany and German-speaking countries and is shaped by various regulations from different areas of law. To date, there is no single, uniform standard covering all applications. Instead, depending on the specific application, building codes, occupational safety laws, hazardous materials regulations, and technical standards all interplay.
The building codes of the federal states form the basis. The Model Building Code (MBO) and the state building codes based on it regulate requirements for storage rooms, fire compartments, and escape and rescue routes. Special building regulations often apply to the storage of large quantities of batteries in buildings, such as in underground parking garages with electric vehicles, commercial warehouses, or industrial facilities. The Technical Rules for Workplaces (ASR) and the Industrial Safety Ordinance (BetrSichV) apply in the commercial sector. For the storage of lithium batteries as hazardous materials, the requirements of hazardous materials law also apply, particularly when large quantities are transported or temporarily stored.
At the standards level, several documents are relevant. The VdS guidelines issued by the German Insurance Association (Gesamtverband der Deutschen Versicherungswirtschaft), particularly VdS 3103 on lithium batteries, provide practical recommendations for storage, charging, and fire safety measures. The VDMA standard sheets and information sheets from the employers’ liability insurance associations, such as the DGUV, round out the picture for commercial applications. The DIN VDE series of standards governs electrical safety aspects of battery systems. For stationary energy storage systems, such as those used in building services engineering, DIN EN IEC 62619 applies, which specifies safety requirements for lithium cells and batteries in stationary applications.
It is important to note that compliance with these regulations does not automatically guarantee complete fire protection. Standards describe minimum requirements based on the state of the art at the time they were developed. Since battery technologies and their fields of application are evolving rapidly, close coordination with the relevant fire safety authority, the insurer, and an experienced fire safety planner who assesses the specific risks of the respective project is recommended.
Structural Requirements for Storage Rooms and Charging Infrastructure
The structural requirements for rooms where batteries are stored or charged are derived from the specific fire characteristics of these energy storage devices. As a general rule, the greater the amount of stored energy, the higher the requirements for fire resistance, smoke extraction, and firefighting readiness. For small quantities—such as a few device batteries in an office—the requirements are manageable. For e-bike batteries in storage rooms, power tool batteries in warehouses, or large-scale stationary storage systems in utility rooms, the requirements increase significantly.
Storage areas for larger quantities of batteries should be designed as separate fire compartments, separated from adjacent areas of use by walls and ceilings with sufficient fire resistance. The fire resistance class depends on the building class and the amount of energy stored. As a guideline, partition walls separating these areas from areas requiring protection should have a fire resistance rating of at least F 90 (REI 90 according to European classification). Doors and gates in these walls must be designed as fire-rated doors and be self-closing. Openings for cables and conduits must be fitted with certified fire barriers to ensure that the fire compartment remains intact.
Ventilation and smoke extraction are particularly important for battery rooms because thermal runaway produces flammable gases before a flame becomes visible. Battery storage rooms should be mechanically or naturally ventilated to prevent gas buildup. Ventilation openings must be arranged to create cross-ventilation; exhaust vents should be located in the upper part of the room, as many of the released gases are lighter than air. At the same time, ventilation openings must be equipped with fire dampers to prevent smoke from spreading to other areas of the building in the event of a fire.
Additional requirements apply to the charging infrastructure. Chargers and charge management systems must be suitable for the types of batteries used and must not allow overcharging. Electrical installations in battery rooms must comply with the relevant VDE standards; outlets and switches should be located outside the room or at a sufficient distance from the batteries. Charging stations for electric vehicles in underground parking garages require special attention, as these garages generally lack natural ventilation and the fire load from a burning vehicle is extremely high. Here, experts recommend fire suppression systems, enhanced smoke extraction systems, and the separation of charging areas from parking areas by means of fire-resistant clearances or protective walls.
Storage Boxes and Cabinets as a Supplementary Safety Measure
For smaller quantities of batteries, such as in workshops, schools, or offices, specially designed battery storage cabinets and storage boxes offer a practical solution. These containers are made of non-combustible materials, have a defined fire resistance rating, and feature integrated ventilation openings. In the event of a fire, they limit the spread of the fire to the contents of the cabinet and give firefighters time to respond. Some models are equipped with integrated fire suppression systems that activate automatically when temperatures exceed a certain threshold. These solutions do not replace compartmentalization fire protection measures, but they are a useful supplement when structural measures are not possible or would be disproportionate.
Fire Detection Technology and Suppression Systems: Early Detection and Suppression
Early detection is of central importance in battery storage fire protection because thermal runaway can still be halted at an early stage through cooling. Conventional smoke detectors have their limitations here: They respond to visible smoke, but the gas phase preceding a battery fire can already be dangerous before smoke is produced. For battery rooms, fire protection planners therefore recommend the use of heat detectors that respond to rising temperatures, or gas detectors that detect specific fire gases such as carbon monoxide or hydrogen fluoride. Combined multisensor detectors, which monitor smoke, heat, and gases simultaneously, offer the highest level of detection reliability.
The fire alarm control panel should automatically trigger defined measures upon an alarm: shutting down the charging infrastructure, activating the smoke exhaust system, alerting the fire department, and, if necessary, triggering a stationary fire suppression system. For battery rooms with a higher fire load, fixed fire suppression systems are a serious consideration. Water is considered the preferred extinguishing agent for lithium-ion battery fires because it cools the cells and slows the spread of thermal runaway to adjacent cells. Sprinkler systems that respond to heat sensors can be effective in battery rooms but must be designed for the specific fire load: The required volume of extinguishing water is significantly higher for battery fires than for conventional fires.
Gas suppression systems, which are commonly used in conventional electrical installations, are only partially suitable for battery fires. They can smother a flame but cannot stop the exothermic reaction inside the cell. After a gas suppression system is triggered, thermal runaway can continue and, once the suppressant has dissipated, may lead to a flame reigniting. For battery rooms, water is therefore generally preferable to gas as an extinguishing agent, provided the structural requirements for water application are met.
Fire Safety for Battery Storage in Various Building Types
Fire safety requirements for battery storage vary significantly depending on the building type and its use. In residential buildings, the increasing prevalence of e-bikes, e-scooters, and home energy storage systems poses new challenges. E-bike batteries are often stored and charged in stairwells, basements, or storage rooms—that is, in areas that serve as or are adjacent to escape and rescue routes. A battery fire in a stairwell can block the only escape route and therefore poses a particularly high risk. Experts recommend that e-bike batteries not be stored or charged in stairwells or directly adjacent rooms, but rather in separate, well-ventilated rooms equipped with fire-rated doors.
In commercial and industrial buildings, the quantities of batteries are often considerably larger. Power tool batteries, industrial truck batteries, and stationary energy storage systems can store energy in the range of several hundred kilowatt-hours. Here, the requirements for fire compartments, fire suppression systems, and fire alarm technology are correspondingly higher. The workers’ compensation association and the insurer must be involved at an early stage, as their requirements may exceed the minimum standards set by building codes. For industrial trucks with lithium-ion batteries used in warehouses, the relevant technical guidelines recommend dedicated charging rooms equipped with fire-resistant partitions, smoke extraction, and a fire suppression system.
Underground parking garages with charging stations for electric vehicles are a separate, intensely debated topic. The combination of limited ventilation, high fire load from vehicle batteries, and difficult access for firefighters makes underground parking garages one of the most challenging applications. Several federal states have now formulated specific requirements for underground parking garages with electric vehicles or are working on them. Sprinkler systems, enhanced smoke extraction, and limiting the number of charging points per fire compartment are typical measures that are discussed and required in this context.
Common Mistakes and Misconceptions in Battery-Related Fire Protection
A common mistake is underestimating the amount of energy stored in modern batteries. A single e-bike battery with a capacity of five hundred watt-hours contains enough energy to cause a significant fire if released uncontrollably. An electric vehicle with a battery capacity of fifty to one hundred kilowatt-hours exceeds the fire load of a conventional vehicle many times over. Anyone who equates these energy amounts with conventional fire loads and designs systems accordingly systematically underestimates the risk.
Another mistake is the assumption that a battery that is not being charged poses no fire risk. As described above, a damaged or deeply discharged battery can develop thermal runaway even while in storage. Batteries that have been mechanically damaged—for example, by a fall or impact—should not be stored any longer without first being evaluated by a specialized company. Deeply discharged batteries—that is, batteries that have been discharged below the minimum voltage—should not be recharged but should be disposed of properly.
Fire safety is also often neglected during charging. Charging is the operating condition with the highest risk because it places the greatest thermal and electrical stress on the cells. Batteries should not be left to charge unattended overnight unless a suitable charging infrastructure with monitoring is available. Charging in bedrooms or in rooms without smoke detectors is not recommended for fire safety reasons. Chargers that are not approved for the specific battery type significantly increase the risk of overcharging.
Finally, the need for regular inspection of fire safety measures is often underestimated. Fire doors held open with wedges, fire suppression systems that have not been maintained, and fire alarms with dead batteries render even well-planned fire safety concepts ineffective. Battery Storage: Fire safety is not a one-time planning task, but an ongoing operational responsibility that requires regular inspections, user training, and documented tests.
Storing Batteries: Fire Safety as an Integral Part of Building Design
The storage of batteries from a fire safety perspective is no longer a niche topic that concerns only specialists. With the widespread adoption of electric vehicles, stationary energy storage systems, and battery-powered devices in nearly all types of buildings, the topic has taken center stage in architectural and planning practice. Anyone planning a residential building, an office building, or a commercial property today must ask where and how batteries will be stored and charged, and integrate this consideration into the fire safety concept from the very beginning.
In practical terms, this means: Storage areas for batteries must be designated early in the floor plan and not treated as leftover space to be addressed later. Their requirements for fire resistance, ventilation, smoke extraction, and fire suppression readiness must be taken into account during the design phase, as retroactive adjustments can be disproportionately costly. Coordination with fire safety authorities, insurers, and the fire department should take place early on, as their requirements often exceed the minimum standards set by building codes and vary depending on the specific project.
Architects and specialist planners who take the topic of fire safety for battery storage seriously make a concrete contribution to the safety of buildings and their occupants. The fire characteristics of lithium batteries are well known, the structural and technical means for risk management are available, and the regulatory framework is continuously evolving. What is often lacking is an awareness that these energy storage systems require a different planning approach than conventional fire loads. Those who understand this difference and take it into account in their planning protect not only the building but also the people who use it.
