How to Design Walk-In Test Chambers for EUCAR Hazard Level 5 EV Battery Safety

Testing high-voltage EV battery packs requires more than controlling temperature and humidity. When a battery test can involve venting, flammable gas release, fire, thermal runaway, or pressure events, the environmental chamber becomes part of the overall safety system.

EUCAR Hazard Level 5 describes a battery test outcome involving fire or flame. It is not, by itself, a chamber design standard or a specification that defines a mandatory set of safety devices.

For test scenarios where fire, gas release, thermal runaway, or pressure events are credible hazards, a walk-in battery test chamber may need to combine environmental control with gas detection, forced exhaust, pressure relief, fire detection and suppression, emergency shutdown, inert-gas systems, reinforced construction, and other application-specific safeguards.

This guide explains how engineers can translate an EV battery test scenario into a practical walk-in environmental test chamber specification, from thermal performance and airflow to safety containment and facility integration.

1. The Thermal Runaway Challenge in EV Battery Testing

EV battery packs are becoming larger, more energy-dense, and more complex. At the same time, battery development requires testing under increasingly demanding thermal, electrical, mechanical, and abuse conditions.

A conventional temperature or temperature-humidity chamber is primarily designed to expose a specimen to controlled environmental conditions. The chamber regulates temperature, humidity, airflow, and sometimes rapid temperature changes while the product is monitored during the test.

Battery safety testing introduces a different engineering problem.

A battery under abnormal conditions may release heat and gases rapidly. Depending on the test scenario, the event can involve electrolyte vapor, hydrogen, carbon monoxide, hydrocarbons, smoke, flame, or a sudden increase in pressure. A thermal runaway event can also change the thermal load inside the chamber much faster than the refrigeration system was designed to handle during normal environmental testing.

This means that the chamber cannot be specified only by asking:

“What temperature range do we need?”

The more important question is:

What can happen to the battery during the test, and how should the test system respond if it happens?

That question should drive the chamber design.

2. What Does EUCAR Hazard Level 5 Actually Mean?

The EUCAR hazard classification is commonly used to describe the severity of battery test outcomes. The levels progress from limited or no effect at the lower end toward increasingly severe physical events at the upper end.

For battery safety discussions, several levels are particularly important:

Level 3: Leakage
Level 4: Venting
Level 5: Fire or flame
Level 6: Rupture
Level 7: Explosion

Therefore, EUCAR Hazard Level 5 should not be described as an explosion classification. It refers to a test outcome involving fire or flame, while rupture and explosion are associated with higher levels of the classification.

More importantly, the EUCAR level describes the hazard severity or observed outcome of a battery test. It does not provide a universal equipment specification stating that every Level 5 test must use a particular pressure-relief door, nitrogen system, gas sensor, or suppression technology.

This distinction matters when specifying a test chamber.

A chamber should be engineered according to the actual test conditions and credible failure modes rather than selecting safety hardware simply because a test has been assigned an EUCAR level.

For example, a test involving a large battery pack, high state of charge, external heating, and thermal propagation may require a substantially different safety architecture from a small-cell test, even if the intended test outcome is discussed using the same hazard classification.

3. A Battery Walk-In Chamber Is More Than a Large Environmental Chamber

The simplest way to understand the difference is to compare the engineering objectives.

A conventional environmental chamber primarily provides:

Temperature control → Humidity control → Airflow → Test exposure → Data collection

A battery safety test chamber may need to provide:

Environmental control → Electrical integration → Gas detection → Ventilation → Fire detection → Suppression → Pressure management → Emergency shutdown

The environmental function remains important, but it is only one part of the system.

KOMEG’s battery walk-in test chamber solutions, for example, are designed around large battery testing applications where temperature and humidity control can be combined with application-specific safety features. Depending on the project, configurations can include explosion-proof windows, safety chains, pressure-relief ports, and customized chamber dimensions and temperature/humidity conditions.

The design should therefore begin with the DUT and test scenario, not simply with the required chamber volume.

4. Start With the Test Scenario, Not the Chamber Size

One of the most common mistakes in environmental chamber selection is starting with a statement such as:

“We need a 10 m³ chamber.”

Chamber volume is important, but it is not enough information for engineering a battery safety system.

Before the chamber is designed, the manufacturer should understand the DUT and the complete test profile.

DUT characteristics

The engineering team should provide information such as:

Cell, module, battery pack, or complete battery system
Overall dimensions
Weight
Battery chemistry
Nominal voltage
Energy capacity
State of charge
Number of units tested simultaneously
Fixture and pallet dimensions
Heat generation during charging or discharging

Test conditions

The test specification should also define:

Minimum and maximum temperature
Humidity requirements
Temperature ramp rate
Dwell time
Number of cycles
Charging and discharging conditions
External heating or cooling
Thermal propagation requirements
Required monitoring parameters

Credible abnormal events

The safety design should then consider what could happen if the DUT fails:

Venting
Gas release
Thermal runaway
Fire
Thermal propagation
Pressure increase
Electrolyte release
Electrical short circuit
Sudden increase in heat generation

This information determines the appropriate combination of detection, ventilation, pressure relief, suppression, and emergency controls.

5. Thermal Performance Still Matters

Adding safety systems does not eliminate the fundamental purpose of an environmental test chamber.

The chamber still needs to maintain the required environmental conditions around the battery pack.

Typical design parameters include:

Temperature range

A battery walk-in chamber may be designed for ranges such as:

-40°C to +150°C

or, depending on the application:

-60°C to +150°C

Other ranges can be engineered for specific requirements.

The important point is that these numbers should come from the test protocol. EUCAR Hazard Level 5 itself does not define a universal temperature range.

Temperature change rate

The required ramp rate should also be determined by the test method.

For conventional environmental cycling, a relatively moderate ramp may be sufficient. For rapid thermal cycling or accelerated temperature transitions, substantially higher rates may be required.

The chamber specification should therefore identify whether the stated ramp rate applies to:

Empty chamber conditions
Loaded chamber conditions
A defined thermal load
A specific temperature interval

This distinction is important because a chamber that can reach a specified ramp rate without a load may behave very differently when testing a large battery pack that is actively generating heat.

6. Thermal Load Is Often More Important Than Chamber Volume

A large battery pack can introduce a significant thermal load during charging, discharging, or abnormal operation.

For this reason, two chambers with the same internal volume may require very different refrigeration capacities.

The engineering calculation should consider:

Battery heat generation
Number of DUTs
Fixture mass
Initial DUT temperature
Charging/discharging power
Airflow
Refrigeration capacity
Heat transfer through chamber walls
Required recovery time

A chamber designed only around internal volume may therefore be undersized for a high-power battery test.

For battery applications, thermal load capacity should be treated as a primary specification rather than an afterthought.

7. Gas Detection: What Should a Battery Chamber Monitor?

Gas detection becomes particularly important when the battery chemistry and test conditions can produce hazardous gases.

A monitoring system may include multiple sensors rather than relying on a single gas detector.

Hydrogen (H₂)

Hydrogen is highly flammable and can be released during certain abnormal battery events. Its low molecular weight and relatively high diffusivity also influence sensor placement and ventilation design.

Carbon Monoxide CO)

CO can be associated with battery decomposition and combustion-related events. Continuous monitoring can provide an additional indication of abnormal conditions.

Hydrocarbons and VOCs

Depending on battery chemistry and failure mechanism, volatile organic compounds and hydrocarbon gases may also need to be considered.

Oxygen (O₂)

Where nitrogen inertization is part of the safety strategy, oxygen monitoring can provide information about the chamber atmosphere and the effectiveness of the inerting process.

Large-scale battery testing facilities operated by the European Commission’s Joint Research Centre, for example, use multiple gas-monitoring technologies together with ventilation, nitrogen inertization, pressure-relief systems, and fire-extinguishing measures. This illustrates an important engineering principle: battery safety is normally handled as an integrated system rather than by one safety component.

8. Pressure Relief: Where Does the Pressure Go?

Pressure management is another critical consideration when testing batteries that may experience severe failure events.

A pressure-relief system is intended to provide a controlled path for pressure to escape when an abnormal pressure event occurs.

However, simply adding a pressure-relief opening does not automatically make a chamber “explosion-proof.”

The complete system needs to consider:

Expected pressure event
Relief pressure
Relief area
Relief direction
Exhaust ducting
Door restraint
Structural strength
Internal lining
Adjacent laboratory areas
Personnel protection
Post-event ventilation

The direction of pressure release is especially important.

If a relief opening directs hot gases, flames, smoke, or pressure toward an occupied area, the relief system may create a different safety problem.

Therefore, the pressure-relief design should be coordinated with the building, laboratory layout, ventilation system, and emergency procedures.

Pressure relief is a system-level engineering decision, not simply an accessory added to the chamber.

9. Fire Detection and Suppression

When fire is a credible test outcome, the chamber should be designed with an appropriate fire detection and suppression strategy.

Possible detection technologies include:

Smoke detection
Flame detection
Temperature monitoring
Gas detection
Pressure monitoring

Suppression technology depends on the battery chemistry, test objective, facility requirements, and risk assessment.

The system may incorporate:

Automatic fire suppression
Manual emergency suppression
Fire extinguishing interfaces
Emergency power isolation
Refrigeration shutdown
Ventilation control
Alarm systems

There is no universal suppression technology that should automatically be applied to every lithium-ion battery test.

For example, the appropriate approach for a small-cell abuse test may differ significantly from the approach used for a large EV battery pack.

This is why a battery chamber should be engineered around the specific failure scenario rather than marketed simply as a generic “fireproof chamber.”

10. Nitrogen Inertization: When Is It Appropriate?

Nitrogen inertization can form part of a battery safety strategy when reducing oxygen concentration is appropriate for the anticipated hazard.

A typical safety sequence might involve:

Hazard detection → Alarm → Electrical isolation → Environmental system response → Ventilation or inertization → Fire suppression → Pressure management → Controlled exhaust

The exact sequence depends on the risk assessment and system architecture.

Nitrogen should therefore not be presented as a universal requirement for EUCAR Level 5 testing.

Instead, the correct engineering question is:

Does inertization provide a meaningful safety function for this specific battery chemistry, test method, failure mode, and facility?

If the answer is yes, the nitrogen system should be integrated with gas detection, oxygen monitoring, control logic, exhaust, and emergency procedures.

11. Airflow Is Both a Thermal and Safety Parameter

Airflow is often discussed in environmental chambers as a temperature-uniformity issue.

For battery safety testing, its role is broader.

Air movement can affect:

Temperature uniformity
Battery cooling
Gas distribution
Sensor response
Exhaust efficiency
Smoke movement
Heat distribution
Fire development

Sensor placement should therefore be considered together with airflow.

For example, placing a gas sensor in a location with poor circulation may delay detection. Similarly, an exhaust system that removes gases effectively but creates undesirable airflow across the DUT may influence the thermal test itself.

This creates an important engineering relationship:

Thermal airflow and safety ventilation cannot always be designed independently.

For large walk-in chambers, computational analysis, airflow testing, or physical validation may be appropriate for complex applications.

12. Heavy-Duty Floor Design for EV Battery Packs

Large EV battery packs can weigh hundreds of kilograms, and some complete battery systems can approach or exceed one metric ton depending on configuration.

The floor therefore needs to be designed around the actual loading conditions.

Engineers should consider:

Static DUT weight
Fixture weight
Pallet weight
Concentrated loads
Wheel loads
Pallet jack loads
Forklift access
Impact loads
Load distribution
Anchoring requirements

Instead of specifying a generic floor-loading number for every project, the better approach is to calculate the required structural capacity from the actual application.

A chamber designed for a battery pack on four concentrated support points, for example, has a different structural requirement from one supporting a uniformly distributed pallet.

For this reason, floor loading should be treated as a project-specific engineering parameter.

13. Electrical and Data Integration

Battery testing usually requires more than environmental exposure.

A battery pack may need to remain connected to:

Battery cyclers
BMS systems
Power supplies
Voltage measurement systems
Current measurement systems
Thermocouples
Pressure sensors
Gas monitoring systems
Cameras
Data acquisition systems
CAN or Ethernet networks

The chamber therefore needs suitable cable ports and interfaces.

The location and quantity of cable ports can affect:

Cable routing
Chamber sealing
Airflow
Electrical safety
Maintenance
Fixture design

For a complex battery test system, it is often better to define these interfaces during the chamber design stage rather than adding them after manufacturing.

14. What Standards Should Engineers Consider?

A battery test chamber may interact with several different categories of standards.

They should not all be treated as interchangeable.

Battery and vehicle standards

Depending on the application, engineers may need to consider standards and regulations such as:

UN 38.3
UL 1642
UL 2580
IEC 62133
IEC 62619
UN ECE R100

These documents address different battery types, applications, and test objectives.

Environmental testing

Environmental conditions may involve standards from the IEC 60068 series and automotive environmental testing standards such as ISO 16750.

For temperature-change testing, for example, IEC 60068–2–14 specifically addresses change-of-temperature testing and the effects of specified ambient temperature changes on specimens.

Energy storage fire testing

For stationary energy storage systems, standards and test methods such as UL 9540A may become relevant. However, UL 9540A should not automatically be treated as a requirement for every EV battery test because its scope is focused on thermal-runaway fire-propagation characteristics of battery energy storage systems.

The correct approach is therefore:

Identify the applicable test standard first, then design the chamber around the environmental and safety conditions required by that test.

15. A Practical Specification Checklist

When discussing a custom walk-in EV battery chamber with a manufacturer, the specification can be divided into five groups.

Environmental performance

Temperature range
Humidity range
Temperature ramp rate
Temperature uniformity
Temperature recovery
Thermal load capacity
Airflow requirements

Chamber construction

Working volume
Door dimensions
Floor loading
Interior materials
Insulation
Observation windows
Cable ports
Lighting

Battery safety

H₂ detection
CO detection
Hydrocarbon/VOC detection where required
O₂ monitoring where required
Smoke/flame detection
Pressure relief
Exhaust system
Fire suppression
Nitrogen inertization where appropriate
Emergency shutdown
Safety interlocks

Test integration

Battery cycler
BMS
DAQ
CAN/Ethernet
Cameras
Gas monitoring
Data logging
Alarm system

Facility requirements

Electrical supply
Cooling water, if required
Exhaust duct
Nitrogen supply
Fire protection
Drainage
Floor loading
Transport route
Ceiling height
Emergency access

This checklist also explains why battery walk-in chamber projects should normally be treated as custom engineering projects rather than simple catalog purchases.

16. How to Evaluate a Walk-In Battery Chamber Manufacturer

Price and chamber volume are useful starting points, but they do not tell the whole story.

An engineering team should examine whether the manufacturer can address the complete system.

Thermal engineering capability

Can the manufacturer calculate the required refrigeration capacity based on the actual battery thermal load?

Safety-system integration

Can gas detection, ventilation, pressure relief, suppression, inertization, and emergency shutdown be integrated into one control architecture?

Mechanical engineering

Can the chamber floor, doors, panels, fixtures, and structural components be designed around the DUT weight and loading conditions?

Electrical integration

Can the chamber accommodate battery cyclers, BMS connections, sensors, cameras, and data acquisition equipment?

Customization

Can the manufacturer adapt chamber dimensions, access doors, cable ports, airflow, ramp rates, floor structure, and safety systems to the actual laboratory?

Documentation and validation

A serious project should also clarify what documentation, testing, commissioning, and safety validation will be provided.

The goal is not simply to purchase a chamber.

It is to build a controlled test environment that behaves predictably under both normal and abnormal test conditions.

17. KOMEG Approach to Custom EV Battery Walk-In Test Chambers

KOMEG approaches battery walk-in chamber projects as application-specific environmental test systems rather than simply enlarging a standard climate chamber.

Its battery walk-in solutions can be configured around the requirements of large battery packs and battery systems, including temperature and humidity control, customized chamber dimensions, temperature-change requirements, cable access, and application-specific safety features.

For battery applications where abnormal events are credible, safety configurations can include options such as explosion-proof windows, safety chains, pressure-relief ports, and other customized protection measures.

KOMEG’s battery thermal test chamber solutions can also incorporate safety functions such as H₂/CO detection, pressure relief, inerting, and fire detection or extinguishing systems, depending on the application and engineering requirements.

The important point is that these features should not be selected independently. The chamber, refrigeration system, airflow, gas monitoring, exhaust, pressure management, suppression, electrical interfaces, and control system need to work together as one test environment.

For large EV battery packs, KOMEG can therefore develop customized walk-in configurations based on the DUT dimensions, thermal load, environmental profile, testing conditions, and required safety architecture.

18. What Information Should You Provide When Requesting a Custom Chamber?

A detailed initial specification can significantly improve the engineering process.

Instead of sending only:

“Please quote a 10 m³ explosion-proof battery chamber.”

Provide the following information.

Battery information

Battery type, chemistry, dimensions, weight, energy capacity, voltage, SOC, and quantity.

Test profile

Temperature range, humidity, ramp rate, dwell time, cycle profile, charging/discharging conditions, and test duration.

Thermal load

Expected heat generation from the battery and connected electrical equipment.

Safety scenario

Expected failure modes, gas species, thermal runaway conditions, fire risk, pressure events, and required emergency response.

Facility information

Available room dimensions, door dimensions, ceiling height, power supply, cooling water, exhaust route, nitrogen supply, floor loading, and equipment access.

Monitoring

Required gas sensors, thermocouples, cameras, BMS interfaces, DAQ systems, CAN, Ethernet, or other data connections.

The more complete this information is, the more accurately the chamber manufacturer can determine refrigeration capacity, chamber structure, airflow, safety systems, and facility requirements.

Designing a walk-in test chamber for EV battery safety testing is not simply a matter of increasing chamber volume or adding an explosion-relief port.

The chamber needs to match the actual test scenario: the battery size and energy, temperature profile, electrical conditions, expected failure modes, gas release, fire risk, pressure behavior, monitoring requirements, and emergency response strategy.

EUCAR Hazard Level 5 is useful for describing a test outcome involving fire or flame, but it should not be treated as a standalone chamber design specification. The engineering task is to translate the credible hazards of the test into a coordinated system of thermal control, detection, ventilation, pressure management, fire protection, structural design, and safety interlocks.

For large EV battery packs, this becomes even more important because chamber volume, thermal load, airflow, floor loading, electrical integration, and safety systems all interact.

The right walk-in battery test chamber is therefore not simply a large environmental chamber.

It is an integrated test and safety system designed around the battery and the test — not the other way around.

About KOMEG

KOMEG designs and manufactures environmental test chambers for temperature, humidity, thermal cycling, thermal shock, battery safety, and other reliability testing applications. Its battery testing solutions include customized environmental chambers and walk-in systems developed around specific DUT dimensions, thermal loads, test profiles, and safety requirements.

For EV battery packs and other large-format battery applications, KOMEG can provide customized chamber configurations covering environmental control and application-specific safety integration.

Other Entries

Popular Blogs