The “What-If” Question and the Challenge of Evacuation
The introduction of battery electric buses (BEB) has marked a new era in sustainable public transport. Yet alongside the many benefits, one pressing concern remains: What if a fire breaks out?
While prevention is critical, real-world incidents have shown that fires can develop rapidly in electric buses, leaving passengers and drivers with very limited time to react.
In the Paris BEB fire on April 4th, 2022, the driver successfully evacuated 14 passengers within 20–30 seconds. Just 30–45 seconds later, the entire bus was engulfed in flames. A second fire in Paris on April 29th, 2022, saw smoke turning into full ignition in only 17 seconds. These examples, among many others worldwide, underline the urgency of finding a solution that buys passengers more time.
Evacuation studies show that it typically takes 1.5–2.5 minutes to clear a bus, depending on size and passenger profile. This is especially critical for larger double-deckers or coaches operating at highway speeds, where passengers may be sleeping or have reduced mobility. The harsh truth is that the time available in many BEB fire incidents is far shorter than the time needed for safe evacuation.
This is where Fogmaker’s latest development provides the answer: creating a vital window for evacuation when every second counts.
Introducing the Fogmaker Sectioning Deployment Valve
The new Fogmaker Sectioning Deployment Valve enables targeted suppression in multiple critical compartments of an electric bus—battery packs, engine bay, or auxiliary systems—using one central fire suppression unit.
Once a fire is detected, the valve automatically directs suppression precisely where it is needed. A single Fogmaker unit deployed in a 1 m³ compartment provides up to 2 minutes of sustained suppression. Adding a second unit extends this to 4 minutes—time that can mean the difference between a safe evacuation and disaster.
How Fogmaker Holds Back a Battery Fire
To understand the effectiveness of the Fogmaker system, it is important to return to the fundamentals of fire chemistry.
All fires are gas-phase reactions. For combustion to continue, three elements of the fire triangle must be present: heat, fuel, and oxygen. At the molecular level, the main reactants are hydrogen, carbon, and oxygen—driving a chain reaction that feeds the fire and escalates heat release.
Fogmaker Eco 1, our suppression agent, disrupts this reaction in three scientifically proven ways:
- Rapid Cooling
Water has exceptional heat-absorbing capacity. Raising the temperature of just 1 liter of water by 1°C requires 1 kilocalorie. When dispersed as ultra-fine microdroplets under 105 bar pressure, the surface area of water increases dramatically, allowing energy to be absorbed almost instantly. Mitigates and helps prevent thermal propagation during discharge and lowers surrounding material temperatures. - Oxygen Displacement
Each droplet can expand up to 1,700 times its volume when turning into steam. This expansion pushes oxygen away from the combustion zone, further starving the fire of one side of the fire triangle. - Chemical Interruption
Fogmaker Eco 1 contains a PFAS-free foam additive (3%) and potassium salts, which actively interfere with the chemical chain reaction of combustion. The salts bind with free radicals such as hydrogen and oxygen, breaking the self-sustaining cycle of the fire.
The combination of these mechanisms—cooling, oxygen reduction, and chemical interference—makes Fogmaker uniquely effective against BEB fires. Unlike traditional suppression methods, it directly addresses the energy and chemistry of a battery fire.
Always Independent, Always Ready
Fogmaker’s technology is fully independent of the vehicle’s electrical system. The pressurized suppression agent is stored at 105 bar and deployed via loss-of-pressure through patented high-pressure spray nozzles. This ensures reliable function even if the bus has lost power. The water-based mist is non-conductive, making it safe for use in high-voltage environments.
Another advantage is discharge duration. Fogmaker’s misting system empties gradually over a significantly longer time than competing technologies, ensuring sustained suppression instead of a short, single burst.
Why This Is a Game-Changer for Public Transport
Electric buses are rapidly replacing diesel fleets worldwide. But high-profile fire incidents, especially during charging or depot storage, have created concern among operators, insurers, and regulators.
Fogmaker’s new system bridges the critical gap between the first sign of fire and the time needed for passenger evacuation. In many cases, it can completely extinguish fires in auxiliary compartments before they spread to the battery packs. In charging-related incidents, it delays fire growth long enough for depot sprinklers to activate or emergency services to respond—minimizing material losses and protecting lives.
Insurers remain cautious about BEB risks. With Fogmaker installed, operators can demonstrate that they have taken every measure to implement reactive fire protection, strengthening their position with both regulators and underwriters.
The importance of this innovation is further underlined by research initiatives. RISE, the Swedish research institute, is planning a full-scale BEB fire test where automatic fire suppression systems (AFSS) will play a central role. Fogmaker was the first to commit to participating.
Key Information
- Developed fully in-house by Fogmaker International’s R&D department, building on the simplicity and proven benefits of our original fire suppression system.
- Formal launch at Busworld, Brussels, October 4–9, 2025.
- Trial installations already completed.
Closing the Safety Gap
Fogmaker’s Sectioning Deployment Valve does more than suppress fire—it provides time. Time for passengers to escape. Time for first responders to arrive. Time to prevent a dangerous event from becoming a catastrophe.
For more information or to discuss how the Sectioning Deployment Valve can improve the safety of your electric vehicle fleet, please contact Fogmaker International.