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Glossary · Energy industry & energy transition

Fire protection

Fire protection Battery storage building safety critical infrastructure thermal runaway power system grid operation charging infrastructure

Fire protection comprises all structural, technical-system and organisational measures that prevent fires, detect them early, limit their spread and make firefighting possible. In the energy system, this concerns not only ordinary buildings. It also covers battery storage systems, substations, transformer stations, cable systems, photovoltaic systems, charging infrastructure, data centres, power plants, industrial plants and control centres. The aim is to protect people and animals, emergency responders, property, the environment and the supply that depends on these installations.

In Germany, the basic objectives are set out in building regulations law. Under Section 14 of the Model Building Code (Musterbauordnung, MBO), structures must be arranged, built, modified and maintained so that four objectives are met: the outbreak of a fire is prevented, as is the spread of fire and smoke. In the event of a fire, the rescue of people and animals and effective firefighting must be possible. The MBO is a model regulation. Only the state building codes (Landesbauordnungen) of the 16 Länder are binding; they adopt these objectives but may differ from one another in detail. It is also important what the provision does not require: it does not guarantee that a fire will never occur. It requires prevention and the possibility of rescuing people and extinguishing the fire.

Fire protection is therefore more than fire extinguishers, smoke detectors or a fire service access road. It is a safety architecture. It determines which materials are used, how installations are physically separated, how faults are detected, what switches off automatically, how smoke and heat are vented, which extinguishing agents are available, what information the emergency responders receive and who decides in an emergency. A good fire protection concept considers not only normal operation. It also takes into account disturbances, maintenance, operating errors, ageing, external influences and the case where individual protective measures fail.

In the energy system, fire protection is particularly important because electrical installations concentrate a great deal of power in a small space. Electric current cannot be seen, but the heat from electrical faults certainly can. Possible ignition sources include overloaded cables, loose contacts, short circuits, arcs, defective power electronics, insulation faults, damaged battery cells or overheated transformers. There are also fire loads, that is, combustible materials such as plastics, cable insulation, housings, transformer oil, packaging in technical rooms or combustible building materials. Fire protection must control the interplay of ignition source, fire load and spread path. One can picture it as a triangle: if one corner is missing or well controlled, a fault usually remains local.

Preventive, defensive and organisational fire protection

Technically, a distinction is made between preventive and defensive fire protection. Preventive fire protection acts before a fire starts. It is usually divided into three parts. Structural fire protection includes fire compartments, fire-resistant walls and ceilings, sealing of cable penetrations, distances, non-combustible building materials and escape routes. Technical-system fire protection includes fire alarm systems, gas detection, automatic shutdown, self-activating extinguishing systems, smoke and heat extraction, and lightning and surge protection. Organisational fire protection is described further below. Self-activating extinguishing systems are therefore specified at the planning stage and thus belong to preventive fire protection, even though they only trigger in the event of a fire.

Defensive fire protection comprises firefighting itself, above all by the public fire service or a works fire brigade. It only works if fires are reported in time, access roads and standing areas are reachable, enough extinguishing water is available and the emergency responders know what kind of equipment they are dealing with. For electrical installations, this knowledge is decisive. Voltage, stored energy, toxic smoke gases or fire sources that are hard to reach change the approach. Under DIN VDE 0132, minimum distances from the nozzle apply when extinguishing fires at low-voltage installations: 1 metre with a spray jet and 5 metres with a full jet. This prevents voltage from arcing over to the responder.

Organisational fire protection links planning and operation. It includes maintenance plans, inspection intervals, permits for work involving ignition hazards such as welding, instruction, operating procedures, alarm and emergency plans, reporting chains, documentation, clear responsibilities and drills. Many fires are not caused by a single technical weakness. Usually a chain lies behind them, such as unnoticed ageing, unclear responsibility, insufficient maintenance, incorrect storage or ignored warning signals. Organisational fire protection interrupts such chains earlier.

Distinction from occupational safety, explosion protection and plant safety

Occupational safety protects employees from hazards at work, for example electric shock, heat, falls, hazardous substances or mechanical injuries. Fire protection also protects people. However, it additionally covers buildings, installations, neighbouring property, the environment and the continuation of operations.

Explosion protection deals with combustible gases, vapours and dusts that can form explosive mixtures with air. It plays a role in hydrogen and biogas plants, gas pressure regulating stations, certain industrial processes and batteries. For lithium-ion storage systems, the fire services' technical recommendation states: in intended operation, an explosive atmosphere is not to be expected. Classification into Ex zones is then generally not necessary, unless the manufacturer's risk analysis indicates otherwise. At the start of a thermal runaway, however, ignitable gases can escape, which initially accumulate without burning. These so-called venting gases contain, among other things, carbon monoxide and hydrogen. If they are ignited later, a deflagration or explosion can occur. Explosion protection works with concentration limits, avoidance of ignition sources, ventilation, zones and pressure relief. Fire protection additionally considers fire spread, structural stability, smoke, extinguishing and escape routes.

Plant safety covers the safe design and safe operation of technical installations as a whole. This includes electrical safety, mechanical stability, functional safety, software, protection technology, maintainability and the control of incidents. Fire protection is one part of it. A battery installation can comply with electrical standards and still have a weak fire protection concept, for example if cell-to-cell propagation, smoke extraction or access for the fire service were not adequately considered.

Resilience is also not the same as fire protection. Resilience describes the ability of a system to withstand disturbances and to remain functional or to become functional again quickly. Fire protection contributes to this because it prevents a local fault from becoming a major outage. Whether a power system is resilient, however, also depends on redundancies, grid structure, spare parts, personnel, communication and reconstruction processes.

Why fire protection in the power system is a system issue

Power systems consist of many interconnected installations. A fire in a single technical room can trigger the evacuation of a building, knock out a transformer station, impair a control centre, shut down a charging facility or take a storage system off the grid. For critical facilities such as hospitals, waterworks, data centres, railway power installations or substations, it is therefore not only a matter of property damage, but also of the continuation of essential services.

With electrification, more electrical equipment is entering buildings, neighbourhoods and commercial areas: heat pumps, charging points, battery storage, photovoltaics, inverters and new cable routes. This does not automatically make these installations unsafe. However, planning, installation, maintenance and use are more closely interlinked. An undersized service connection, improper cable routing, a missing disconnection option, poor ventilation or an overloaded sub-distribution board can turn a modernisation into a fire hazard.

For security of supply, the connection is concrete. Fire protection does not prevent every disturbance, but it limits how far and how long it takes effect. Separate technical areas, redundant feed-ins and clear shutdown concepts can ensure that a fire damages one installation but does not paralyse an entire building or site. If an installation fails, the consequential damage can be greater than the fire damage itself, for example with a storage system that provides balancing power or with the charging infrastructure of a bus fleet. Fire protection therefore influences investment costs, insurability, permitting, site selection and operational management.

Battery storage and thermal runaway

With a battery storage system, fire protection is a particular focus because lithium-ion cells can enter thermal runaway in the event of serious faults. This means a self-reinforcing thermal runaway. According to the fire services' technical recommendation, the triggers are mainly three kinds of stress: mechanical damage, such as internal short circuits after impacts; electrical stress, such as overcharging; and thermal stress, such as from a fire in the surroundings. The heat released accelerates further reactions. The cell can eject hot, combustible gases, burn and heat neighbouring cells. The consequences can be rapid fire spread, a great deal of released energy and heavy smoke production.

The real challenge is less the individual cell event than its possible propagation within a module, cabinet, container or battery room. Fire protection for storage systems therefore covers cell chemistry, battery management system, temperature monitoring, electrical protective devices, mechanical separation, fire compartments, ventilation, pressure relief, gas detection, smoke extraction, extinguishing water, access and operational planning. According to the technical recommendation, how a fire develops depends, among other things, on cell type, cell chemistry, state of charge and design. Generally valid requirements are therefore possible only to a limited extent. For second-life batteries, the recommendation points out that, because of their age, there may be a higher risk of cell damage.

A common misconception is that a battery fire can be treated like an ordinary plastic or electrical fire. Even when no flames are visible any more, electrical and chemical energy may still be stored. Cells can heat up again, smoke gases can be toxic and corrosive, and individual cell packs are hard to reach. The fire services name water as the extinguishing agent of choice even for large-scale storage systems, and wetting agents may be added. They generally do not consider special extinguishing agents necessary for the public fire service. The primary aim is to prevent spread to the surroundings and to unaffected storage units. This is done with so-called barrier positions, that is, a water barrier to protect the neighbourhood. Targeted extinguishing and cooling are to be preferred to letting the fire burn out in a controlled manner. However, controlled burn-out can be a practicable option in individual cases after careful consideration. As a guideline for whether cooling is needed, a module housing temperature of about 80 degrees Celsius has proven useful.

Equally wrong is the assumption that batteries are fundamentally uncontrollable. The fire services' technical recommendation considers lithium-ion storage systems sufficiently safe where good manufacturing standards, certified charge and cell monitoring and proper operation are in place. In intended use without external influence, they rarely catch fire. The same recommendation also states soberly: once a fire has taken hold of an installation, the fire service can generally not prevent its total loss. This determines the focus of precaution. A fire from outside should not reach the batteries in the first place, and a fire inside should not spread to neighbouring installations.

The fire hazard of a storage system therefore cannot be read from its capacity in kilowatt-hours alone. Capacity describes the amount of energy stored, but not the whole risk situation. Equally important are cell chemistry, module design, packing density, cooling, state of charge, mode of operation, ageing, fault detection, spatial separation and options for emergency response. A small storage system in an unsuitable cellar can be more problematic than a large, easily accessible and properly separated container outdoors. In practice, recommendations and model regulations nevertheless tie into size thresholds because they are easy to handle.

Fire services' guideline values for large-scale storage

For large-scale lithium-ion storage systems, the joint technical committee of the Working Group of the Heads of Professional Fire Brigades (AGBF) and the German Fire Brigades Association (DFV) has published recommendations. The current version is dated 20 November 2025 and was coordinated with BVES, GDV, VdS and DGUV, among others. The recommendations are not law. However, permitting authorities and fire protection offices often draw on them. Important guideline values are:

  • Distances: To other buildings or objects, 5 to 10 metres are regarded as sufficient according to current knowledge. However, the values must always be set case by case. For open-site installations, the recommendation specifies at least 3, 5 or 10 metres depending on the size of the installation. Solid, non-combustible walls or large-scale fire tests can justify smaller distances if the fire protection office and the property insurer agree.

  • Separation from other equipment: Batteries should be separated from inverters and transformers. Under DIN VDE 0101-1, the distances are generally 3 metres for cast-resin transformers and 5 metres for oil-filled transformers.

  • Extinguishing water: For medium and large installations, at least 800 litres per minute over two hours must be demonstrated, i.e. 96 cubic metres in total. There are currently no building-law requirements for extinguishing water retention. For large installations or sensitive sites, for example in water protection areas, it must be agreed with the authority.

  • Installation in buildings: Fire-resistant solid partition walls, pressure relief to the outside, secured access preferably on the ground floor at an external wall and marking in accordance with VDE-AR-E 2510-2 next to the door are required. Very large storage systems, with 1,000 kilowatt-hours named as an example, can be classified as a special building in individual cases. The building permitting authority decides on this.

  • Site limits: Battery storage systems are generally not possible beneath high-voltage overhead lines because the lines could break in a fire. In garages, storage systems outside of vehicles generally have to be separated from the rest of the garage space in a fire-resistant manner.

For operating rooms, the Model Ordinance on the Construction of Operating Rooms for Electrical Installations (M-EltBauV) additionally applies. According to the technical recommendation, its scope was extended to energy storage systems in spring 2022. Excluded are free-standing storage systems outside buildings, storage parks and home storage systems below 20 kilowatt-hours. Whether and in which version a Land has adopted this model rule must be checked in the respective state law. For photovoltaic systems with home storage, there is a separate technical recommendation of the fire services from November 2023. It points out that, depending on state law, PV systems are often exempt from building-permit procedures, but that emergency responders can nevertheless be exposed to additional hazards in the event of a fire.

Electrical faults: short circuit, arc and overheating

Electrical installations usually become a fire risk through heat. In a short circuit, very high currents flow, which have strong thermal and mechanical effects within a short time. Fuses, miniature circuit breakers and circuit breakers are meant to disconnect such faults quickly. Whether this succeeds depends on correct sizing, coordination of the protective devices with one another (selectivity), sufficient breaking capacity, an intact installation and regular testing.

Arcs are particularly dangerous because they become very hot and can ignite combustible material. They arise, for example, from damaged insulation, loose contacts, contamination, moisture, ageing or faulty assembly. In installations with direct current, such as on the module side of photovoltaic systems or in battery systems, arcs are harder to extinguish than with alternating current. The reason: direct current has no natural zero crossing at which the arc could break off by itself. High-quality connectors, careful cable routing, well-thought-out shutdown concepts and arc detection are therefore particularly important here.

Overheating often develops inconspicuously. Loose screw connections, overloaded or tightly bundled cables, dirty ventilation openings, defective fans or overloaded transformers heat up without a protective device immediately tripping. Thermography, that is, thermal imaging measurement, as well as maintenance, load management and clean documentation are therefore practical fire protection tools. They do not fight the fire, but its precursors.

With charging infrastructure, high power flows over longer periods in publicly or semi-publicly accessible areas. Fast-charging points, depot chargers and charging parks combine grid connection, power electronics, cables, plugs, communication, vehicles and user behaviour. Fire protection must clarify here how the vehicles are arranged, which distances to buildings apply, how faults are detected, how the installation can be de-energised and how the fire service reaches the location of the fire.

Structural measures: fire compartments, distances and accessibility

Structural fire protection decides whether a fire remains locally contained. Fire compartments separate rooms or parts of installations so that fire and smoke do not spread across for a defined time. How long walls, ceilings, doors, cable seals and ventilation dampers withstand a fire (fire resistance duration) determines how much time remains for evacuation, shutdown, response and damage limitation.

Outdoors, distances take on this task. Storage containers, transformers, charging parks or emergency power generators can be arranged so that thermal radiation, flame spread and smoke do not directly hit neighbouring installations. This is particularly important when several installations of the same kind stand next to one another. If a fire threatens all parallel components at once, the redundancy exists only on paper. Several transformers or storage units at one site help little if, in fire protection terms, they act like a single unit. In the substation, too, fire walls, oil collection pits and distances between transformers are therefore used. For substations, the fire brigade associations have a separate technical recommendation (2024-03), to which the storage recommendation refers.

Accessibility is often underestimated. An installation can in theory be shut down, monitored and extinguished, and in an emergency still be hardly reachable. Narrow technical rooms, locked gates without fire service access, missing access roads, unclear signage, incomplete plans or blocked areas delay the response. For outdoor storage parks, the fire services recommend paved access roads at least 3.5 metres wide, based on the guideline on areas for the fire service. Site inspections together with the operator are also recommended. Especially for critical infrastructure, fire protection must work even under poor conditions: at night, in smoke, during a power outage and with emergency responders who do not know the installation.

Technical protection systems and their limits

Technical-system fire protection includes fire alarm systems, alerting, automatic shutdown, extinguishing systems, smoke and heat extraction, ventilation, pressure relief, temperature and gas monitoring, and control technology. These systems only work if they match the hazard. A smoke detector may respond late if a battery event initially begins only with escaping gases. An extinguishing system can slow the spread, but does not remove the energy in the system. A fire alarm system can disconnect the storage system from the grid or from a photovoltaic system. The energy in the cells nevertheless remains.

It is therefore necessary to distinguish between disconnection and freedom from hazard. A photovoltaic system continues to carry direct voltage in daylight. A lithium-ion battery remains live after emergency shutdown, as the fire services' technical recommendation expressly points out. Capacitors in power electronics can hold residual voltages. Emergency responders and maintenance personnel therefore need clear markings, circuit diagrams and safe procedures. If components have to be dismantled after a fire, this should be done by an instructed electrically qualified person. Fire protection does not end at the main fuse.

Automatic extinguishing systems are also not a panacea. Sprinkler, fine-spray or water-mist systems and inert gas, aerosol and foam systems work differently. Water cools, but can produce contaminated extinguishing water. Inert gases reduce the oxygen content in the room. They work only in largely enclosed rooms, endanger people during flooding and hardly cool battery cells. Aerosols can inhibit flames but do not solve the cooling problem. According to the technical recommendation, such systems for storage often go beyond building regulations law. They are often installed at the request of the operator, who wants to secure installation availability, or at the demand of the property insurer. Which system is suitable depends on the type of fire, room geometry, danger to persons, risk of re-ignition, environmental requirements and maintainability.

Protection systems can also fail themselves. Sensors become dirty, fans fail, extinguishing agent containers lose pressure, software is set incorrectly. A protection concept that relies on a single protection layer is therefore too weak. Multi-level concepts combine avoidance, early detection, shutdown, containment, extinguishing and emergency response organisation.

Responsibilities and permitting practice

Fire protection is also a question of responsibilities. Building owners, operators, planners, installers, manufacturers, experts, insurers, grid operators, authorities and fire services have different roles. The manufacturer supplies safe components but is not automatically responsible for the site. The installer installs in accordance with standards but does not monitor later operation. The fire service gives operational advice but does not replace fire protection planning. The operator remains responsible for maintenance, access, documentation and operational organisation.

Which rules apply depends on the installation. In Germany, these include the state building codes with their special-building and operating-room ordinances, the Technical Building Rules, workplace, industrial safety and hazardous substances law, environmental and water law, as well as VDE provisions and DIN standards. In addition there are non-statutory rule sets such as VdS guidelines, insurance conditions, technical recommendations of the fire services and industry guidelines, for example the safety guideline of the German Energy Storage Association (Bundesverband Energiespeicher Systeme, BVES) for large-scale storage. In the permitting procedure, a fire protection verification is generally required for storage construction projects. The technical recommendation also advises coordinating early with the property insurer, as the insurer may impose additional requirements.

It becomes difficult when new technology spreads faster than administrative routines develop. Home storage systems, commercial battery systems, charging parks, neighbourhood storage or second-life batteries do not always fit into existing categories. Questions then arise early: Which authority is responsible? Is the installation treated as technical building equipment, as an operating room, as storage or as a special building? Which documents does the fire service need? Which distances does the insurer require? Delays often arise not because anyone rejects the technology, but because the interfaces between planning, permitting, operation and emergency response are unresolved.

Costs, liability and insurability

Fire protection costs money and is sometimes portrayed in debates as an additional burden of the energy transition. For investors, operators and insurers, however, it is one of the real system costs. An installation that appears cheaper without sufficient separation, detection, maintenance or an extinguishing water concept merely shifts the costs into the damage risk. In the event of a fire, they are then borne by owners, insurers, neighbours, emergency responders or public infrastructure.

Insurability is a good touchstone. Insurers look at probability of occurrence, extent of damage, accumulation risks (many losses from one event) and operational organisation. A storage system with distance to buildings, tested technology, early fire detection, a fire service plan and a maintenance contract is assessed differently from a retrofitted installation without documentation. After a fire, it is also examined whether planning, installation, operation and maintenance complied with the recognised rules. Missing test records, overlooked warning messages or unapproved modifications can weigh more heavily than the technical defect itself. Fire protection is therefore also a question of demonstrability.

Typical misunderstandings

  • Fire protection comes last: For storage systems, charging parks, substations or industrial plants, a fire protection concept added afterwards often leads to expensive changes. Location, room size, distances, pressure relief, cable routing, escape routes, extinguishing water and shutdown help determine the technical design and therefore belong at the beginning of planning.

  • Compliance with standards means complete safety: Standards describe minimum requirements and test procedures for typical cases. They do not replace a hazard assessment for the specific site. The fire services' technical recommendation also stresses that the individual case must always be examined closely.

  • No water on electrical fires: This statement is too crude. Live equipment poses particular dangers, but with the nozzle distances under DIN VDE 0132, extinguishing with water is possible. For batteries, water is even the preferred cooling and extinguishing agent. Decisive are voltage level, design, accessibility, contamination and retention.

  • Every fire is a catastrophe: Good planning can confine a fire to a cabinet, room, container or fire compartment. Conversely, a small defect can have major consequences if it occurs at a central node without separation, redundancy or an emergency plan.

  • Spectacular individual cases show the typical risk: A factual assessment requires event rates, operating hours, installation types, cell chemistries and extent of damage. Low probabilities of occurrence must not, however, play down difficult operating conditions either. Fire protection always considers both, probability and consequences.

Fire protection as a prerequisite for flexibility and decentralisation

Electricity supply is becoming more fine-grained and more strongly shaped by power electronics. Photovoltaics, home and neighbourhood storage, charging infrastructure, heat pumps, electrolysers and industrial load management multiply the number of electrical operating points. Many of these installations provide flexibility because they shift consumption, storage or feed-in in time. This only helps if the installations are permitted and remain in operation permanently. A storage system that is not permitted because of missing safety verification, or that stands idle for a long time after an incident, can neither ease grid bottlenecks nor provide balancing power. Fire protection thus indirectly decides how much storage power and storage capacity is actually usable.

In grid operation, fire protection has an operational side. Substations, switchgear, cable routes and transformers are nodes where a fire can hit several circuits, protection systems or communication paths at the same time. Grid operators therefore plan spatial separations, oil collection pits, fire walls, automatic alerts, backup switching and emergency processes. For high- and extra-high-voltage installations, it is not only about extinguishing. It is also about safe shutdown, the stability of the rest of the grid and tested reconnection. Because electrical equipment ages under load, load management can reduce fire risks if it avoids overloads. It can, however, create new risks if installations more often reach operating states for which they are not thermally designed.

What fire protection makes visible and what it does not

Fire protection shows that energy technology is embedded spatially, materially and organisationally. A kilowatt-hour in a storage system, a charging point in a car park or an inverter in a technical room are at a concrete location. There, electrical power, materials, people, weather, maintenance, insurance conditions and response options come together.

Whether a technology makes sense in energy-economic terms is not answered by fire protection alone. A storage system can be well planned in terms of fire protection and still be uneconomical. Fire protection assesses one particular type of hazard and how it is controlled. It does not replace an analysis of economic viability, grid compatibility or climate impact. Nor is it suitable as a blanket argument against new technology. Oil boilers, gas pipelines, coal conveyor belts, transformers, cable shafts and tank farms also have fire risks. The sensible question is not whether an installation can burn at all. The sensible question is which faults are realistic, how they are detected, how far they can spread and who remains able to act in an emergency.

Fire protection is thus a touchstone for the quality of technical integration. It shows whether an installation is regarded as an isolated device or as part of a building, an operation, a grid node and an emergency response environment. Good fire protection planning does not reduce the risk to zero. But it ensures that faults remain contained, responsibilities are clarified, emergency responders do not have to improvise and supply outages do not become unnecessarily larger.

Sources

Related glossary entries

Edited by eCMS on 11.11.2026 16:20

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