Time to retire submersion tactics: Why water tanks fail to stop lithium-ion battery incidents
Iain Hoey
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Neil Pedersen, CEO at Fire Containers limited, explains why submersion tactics are ineffective and how targeted containment units offer a safer and more sustainable alternative
As the global transition to electric vehicles (EVs) accelerates, so too does the challenge of safely managing lithium-ion battery incidents, particularly in post-collision or fire-related recovery scenarios.
For years, one of the most commonly discussed methods for handling runaway battery fires has been full submersion in water.
Yet, while this may appear on the surface to offer a reliable solution, the reality is far more complex – and dangerous.
It is time the industry confronts an inconvenient truth: submersion tactics are not only outdated, but they pose significant safety, environmental, logistical, and cost-related risks.
Instead, advanced water suppression containment systems – such as those utilised in purpose-built containment units – offer a far more effective, scalable, and environmentally responsible alternative.
The myth of submersion
Submersion is often marketed as a “catch-all” solution: place the burning or compromised EV in a large container, flood it with water, and let it sit until the risk has passed.
On paper, it sounds logical.
In practice, it’s riddled with flaws.
1. Size and impracticality
A typical electric vehicle weighs between 1.5 to 3 tonnes and is roughly 4–5 metres long.
Submerging such a vehicle requires a container large enough to fully engulf it in water, filled with tens of thousands of litres.
This volume is not only difficult to access in most real-world recovery scenarios, especially roadside or in urban areas, but also impossible to mobilise quickly without significant delay and infrastructure.
2. Environmental hazards
Lithium-ion battery fires release toxic and corrosive gases, and when these batteries are submerged, the water rapidly becomes contaminated with heavy metals, fluorinated compounds, and harmful particulates.
This produces a hazardous waste by-product that must be disposed of as chemical waste – at high environmental and financial cost.
Spillages or improper containment can lead to serious ecological damage.
3. Fire re-ignition risk not resolved
The common belief that submersion ‘kills’ the fire is misleading.
Lithium-ion battery cells can undergo thermal runaway – a self-sustaining chemical reaction that doesn’t rely on oxygen.
Water may cool the battery temporarily, but cells can reignite hours or even days later, especially once the submerged vehicle is removed.
Submersion delays, but does not neutralise, the root problem.
4. Logistics and transport challenges
Once submerged, how do you move the vehicle? Most recovery operators do not carry 30,000-litre submersion tanks.
Transferring the vehicle between the scene, a submersion tank, and a disposal site increases the risk of cell re-ignition, environmental leakage, and injury.
It also escalates operational complexity beyond what recovery teams or emergency responders are trained or equipped to manage.
The case for water suppression containment
Rather than trying to extinguish thermal runaway through sheer volume, a smarter, safer method lies in controlled suppression within purpose-built containment systems – designed to isolate, cool, and control the event while supporting emergency response and recovery.
1. Engineered for real-world application
Water suppression containment units – such as the Fire Safety Containment Unit (FSCU) and Electric Vehicle Containment Unit (EVCU) developed by Fire Containers limited – are designed specifically to handle EV incidents.
These mobile units can be deployed at the scene, allowing immediate containment without moving the vehicle over long distances or waiting for specialist tanks.
2. Targeted water mist technology
Unlike brute-force submersion, these units use high-efficiency water mist suppression systems.
Fine water droplets rapidly absorb heat and cool the battery casing, suppressing flames and preventing escalation.
Water is applied directly to the risk zone, minimising waste and environmental runoff.
3. Continuous suppression with water recycling
Advanced units incorporate recycling sumps and filtration systems, allowing for continual suppression without requiring thousands of litres of clean water.
Contaminated water is captured, filtered, and reused within the sealed system – protecting the environment and drastically reducing disposal costs.
4. Sealed and safe transport
Unlike submersion tanks, water suppression containment units are built to comply with ADR regulations, meaning they are legal and safe to transport hazardous goods.
The vehicle remains sealed within the unit – under suppression and observation – during its journey to a secure facility.
This reduces the need for on-site firefighting and protects recovery operators from toxic exposure.
5. Supporting ESG goals
With governments and industries focusing increasingly on Environmental, Social, and Governance (ESG) standards, submersion methods stand in stark contrast to sustainability goals.
Water suppression containment offers a cleaner, more sustainable, and auditable solution, reducing environmental impact and aligning with waste reduction strategies.
The industry needs a shift in thinking
Emergency services, recovery companies, insurance providers, and transport agencies must move away from improvised submersion tactics and embrace engineered solutions.
What we need is not more water – but better strategy.
Submersion tactics were born from necessity during the early days of EV fires when no better options existed.
But times have changed. Technology has evolved.
The dangers of submersion – environmental contamination, inefficient suppression, re-ignition risk, and legal liability – now far outweigh the benefits.
Water suppression containment units offer a scalable, mobile, and environmentally responsible method for lithium-ion battery recovery and containment.
They protect people, property, and ecosystems – while delivering operational efficiency and compliance.
Final thought
As electric vehicles continue to dominate our roads, the incidents involving lithium-ion batteries will only increase.
We cannot afford to rely on outdated or harmful tactics.
It is time the industry recognises that submersion is not a solution – it’s a liability.
Water suppression containment is not only the best option.
It is the only responsible option.