As a fire investigator, you’re likely to come across an increasing number of incidents involving electric vehicles (EVs). The fire behavior presented by EVs differs significantly from traditional internal combustion engine (ICE) vehicle fires. With the growing adoption of EVs, understanding these differences is important so you can adapt your methods, ensure accurate analysis, and use the right safety protocols.
In this article, we’ll look at the key differences between EV and ICE vehicle fires so you’ll have the knowledge and tools needed to tackle these challenges.
8 Key Differences Between EV and ICE Vehicle Fires
Investigating EV fires is very different from traditional vehicle fires. Let’s take a closer look at what makes them so different.
| Key Difference |
EV Fires |
ICE Fires |
| Fire Frequency |
25 fires per 100,000 vehicles (2023) |
1,500 fires per 100,000 vehicles annually |
| Ignition Source |
Battery-related issues (e.g., thermal runaway) |
Fuel leaks, electrical malfunctions |
| Temperature Range |
Exceeds 1,200°F |
Peaks around 600°F |
| Combustion Duration |
Prolonged with potential reignition |
Shorter, extinguishes once fuel is consumed |
| Toxic Emissions |
Hydrogen fluoride, methane, and carbon monoxide |
Carbon monoxide, hydrocarbons, and nitrogen oxides |
| Suppression Methods |
Requires extensive water or specialized agents |
Traditional methods like water or foam suffice |
1. Fire Frequency and Risk
A stark difference emerges when you compare the frequency of EV and ICE vehicle fires. ICE vehicles experience fires at a significantly higher rate, with approximately 1,500 fires per 100,000 vehicles annually. These incidents are often due to the volatility of gasoline and diesel fuels, coupled with the high operating temperatures of internal combustion engines.
In contrast, EVs are far less likely to catch fire, with only 25 fires per 100,000 vehicles reported in 2023. The reduced fire rate is attributed to the absence of flammable liquids and the advanced safety measures integrated into EV battery packs. But, when EV fires do occur, they are far more complex and challenging to manage.
It’s also interesting to note that fire incidents in hybrid vehicles occur at a far greater rate of 3,475 fires per 100,000 vehicles.
2. Ignition Sources
The ignition sources of EV and ICE fires are also very different, with each presenting unique evidence patterns and challenges.
Internal Combustion Engine Fires
In ICE vehicles, fires are usually caused by fuel leaks, electrical malfunctions, or overheating engines. A ruptured fuel line can release flammable liquids onto hot surfaces, sparking a fire. Electrical malfunctions in wiring systems often leave signs of arcing or melted insulation near the ignition point. These fires typically spread quickly but are easier to suppress once the fuel source is depleted.
Electric Vehicle Fires
EV fires usually originate in the battery pack. Here are the main ignition triggers:
- Thermal Runaway: This chain reaction starts when one cell overheats, spreading heat to neighboring cells and resulting in combustion.
- Physical Damage: Collisions or punctures can compromise the battery's structural integrity, leading to internal short circuits.
- Faulty Charging Equipment: Electrical faults caused by defective chargers or overvoltage can lead to overheating.
As an investigator, you’ll need to do a detailed burn pattern analysis and examine the battery remnants to identify the initial failure point and pinpoint the ignition source in EV fires.Electric School Bus Fire: Are Drivers Prepared for the Risks?
3. Combustion Behavior
The combustion behavior of EV and ICE fires also differs in terms of intensity, duration, and suppression challenges.
Electric Vehicle Fires
EV fires are characterized by extreme temperatures exceeding 1,200°F. As the battery cells rupture, they release flammable gases like hydrogen and methane, which intensify the fire. These fires often produce explosive bursts and thick toxic smoke. This can be a significant hazard to responders. Additionally, EV fires can reignite hours or even days later due to residual energy in the undamaged cells.
Internal Combustion Engine Fires
ICE fires, in contrast, tend to burn predictably. Fueled by gasoline or diesel, the flames usually spread outward from the engine compartment. Once the fuel source is consumed, the fire extinguishes naturally, with temperatures peaking at around 600°F. These fires are less intense and easier to manage with conventional suppression methods.
4. Burn Patterns and Evidence
Every fire leaves behind burn patterns, which can provide important insights into the origin and cause of the fire. Burn patterns differ significantly between EV and ICE fires.
EV Fires
Burn damage in EVs is often concentrated around the battery compartment or electrical systems. The intense heat from thermal runaway creates localized charring and ruptured battery cells, which can serve as key evidence. You should focus on identifying the module or cell where the fire originated, as this can provide clues about the cause, such as a manufacturing defect or an overcharging incident.
ICE Fires
In ICE vehicles, burn patterns are typically found near the engine or fuel system. Investigators may observe soot trails leading from leaking fuel lines or melted components around the ignition source. Electrical fires within ICE vehicles often leave behind arcing marks and localized burn damage in the wiring system.
5. Toxic Gas Emissions
Both EV and ICE fires release hazardous gases, but the composition and risks vary greatly.
Electric Vehicle Fires
EV fires emit a mix of toxic and flammable gases, including:
- Hydrogen Fluoride (HF): A corrosive gas that causes severe burns and respiratory distress.
- Methane and Hydrogen: Flammable gases that can lead to explosions.
- Carbon Monoxide (CO): A common byproduct of combustion.
For EV fires, advanced gas detection equipment and full respiratory protection are important to ensure your safety on the scene.
Internal Combustion Engine Fires
In ICE fires, emissions are dominated by carbon monoxide, hydrocarbons, and nitrogen oxides. While dangerous, these gases are more familiar to investigators and first responders, making them easier to anticipate and mitigate.
6. Suppression Challenges
The suppression methods required to extinguish EV and ICE fires also highlight another major difference.
EV Fires
EV fires are notoriously difficult to suppress. Traditional methods like water may not suffice, as the intense heat of lithium-ion batteries can sustain combustion. Specialized agents, such as Class D extinguishers or large volumes of water for prolonged cooling, are often necessary. You must also account for the possibility of reignition, which can occur long after the fire is extinguished. ICE FiresSuppression techniques for ICE fires are more straightforward. Water, foam, or dry chemical agents are typically effective in extinguishing the flames once the fuel source is eliminated.
7. Reignition Risks
Reignition is a significant challenge in EV fires due to residual energy in undamaged battery cells. This requires constant monitoring of the scene using thermal imaging cameras to detect hotspots and prevent further incidents. In ICE fires, reignition is rare and typically occurs only if fuel leaks are left unaddressed. This difference highlights why you need specialized post-fire protocols in EV fire investigations.
8. Investigative Tools and Approaches
You must adapt your tools and techniques to handle the unique challenges posed by EV and ICE vehicle fires. This will allow you to ensure accurate cause determination and evidence preservation. EV Fires
- Use thermal imaging cameras to identify residual heat and potential reignition risks.
- Leverage data from the vehicle’s Battery Management System (BMS) to uncover pre-fire conditions such as voltage spikes or overcharging.
- Conduct chemical analyses of toxic gas emissions to identify key combustion byproducts.
ICE Fires
- Focus on physical evidence, such as heat damage near the engine or fuel system.
- Examine wiring systems for signs of electrical shorts or arcing.
FAQs
What is the difference between EVs and internal combustion engine fires?
Electric vehicle (EV) fires and internal combustion engine (ICE) fires differ in several critical ways. EV fires are typically caused by battery-related issues, such as thermal runaway, while ICE fires often result from fuel leaks or engine malfunctions.
EV fires can reach temperatures over 1,200°F, making them more intense than ICE fires, which peak at around 600°F. Additionally, EV fires produce toxic gases like hydrogen fluoride and methane, while ICE fires primarily emit carbon monoxide and hydrocarbons. The suppression of EV fires is more challenging, often requiring specialized agents and prolonged efforts, compared to ICE fires, which can be extinguished with traditional methods like water or foam.
Are EV fires harder to put out?
Yes, EV fires are significantly harder to put out compared to traditional ICE fires. The main challenge is in the behavior of lithium-ion batteries, which can sustain a chemical reaction known as thermal runaway.
This reaction continues even when external flames are extinguished, causing the fire to reignite hours or days later. Also, the compartmentalized design of EV battery packs traps heat and flammable gases, which prolongs combustion. Suppression often requires tens of thousands of gallons of water or specialized extinguishing agents, and even then, reignition remains a persistent risk.
How common are EV fires compared to ICE fires?
EV fires occur far less frequently than ICE fires. According to recent data, EVs experience about 25 fires per 100,000 vehicles, compared to 1,500 fires per 100,000 ICE vehicles annually. While less common, EV fires are more complex and challenging to manage due to factors like high temperatures, toxic gas emissions, and prolonged combustion.
What vehicles catch fire the most?
Internal combustion engine vehicles account for the majority of vehicle fires worldwide, primarily due to their prevalence and reliance on flammable fuels like gasoline and diesel. Fuel leaks, electrical malfunctions, and engine overheating are common causes of these fires.
Electric vehicles, though less prone to fires overall, present unique challenges when they do ignite. Among EVs, larger vehicles with high-capacity battery systems, such as electric buses and commercial fleet vehicles, are at higher risk due to the increased potential for thermal runaway and the complexity of their battery designs. Hybrid vehicles, which combine both ICE and EV components, can also pose unique fire risks due to the interplay of traditional and battery-related hazards.
