Electric Vehicle Fire Risks in Underground Garages: A Critical Analysis
As electric vehicles (EVs) continue to gain traction across global markets, their integration into urban infrastructure has introduced new challenges for fire safety, particularly within underground parking facilities. With increasing numbers of EVs being charged in confined subterranean environments, concerns over fire hazards have escalated among fire safety experts, urban planners, and emergency response teams. A recent in-depth study by Deng Xiaojun from the Yacheng District Fire and Rescue Brigade, Sichuan Provincial Fire and Rescue Corps, published in Building Fire Protection (January 2024), sheds light on the specific fire risks associated with electric vehicles parked and charged in underground garages. The research provides a comprehensive analysis of battery technologies, fire causation mechanisms, fire behavior in enclosed spaces, and actionable strategies for emergency response and prevention.
The transition from internal combustion engine vehicles to electric mobility is widely celebrated for its environmental benefits and long-term sustainability. However, this shift brings with it a new set of technical and operational risks—chief among them being the potential for battery-related fires. Unlike conventional vehicle fires, which typically involve fuel and engine components, EV fires originate primarily from lithium-ion battery systems. These high-energy-density power sources, while efficient and lightweight, are susceptible to thermal runaway—a self-sustaining chain reaction that can lead to rapid ignition, intense heat release, and prolonged combustion. When such events occur in underground parking structures, the consequences can be significantly more severe due to the unique architectural and environmental constraints of these spaces.
Deng Xiaojun’s study begins with a detailed examination of battery types used in modern electric vehicles, emphasizing the dominance of lithium-ion technology. Compared to traditional lead-acid or nickel-metal hydride batteries, lithium-ion cells offer superior energy density, longer cycle life, and reduced weight—key advantages that have made them the preferred choice for EV manufacturers. However, these same attributes contribute to their inherent instability under certain conditions. The research highlights that lithium-ion batteries are particularly vulnerable to overcharging, deep discharging, internal short circuits, and mechanical or thermal damage—all of which can trigger exothermic reactions leading to fire or explosion.
One of the central findings of the paper is the identification of common failure points in EV charging systems that may initiate fires. Faulty charging cables, degraded connectors, poor socket design, and malfunctioning charging controllers were cited as primary contributors to electrical faults. Arcing at connection points, especially in older or poorly maintained infrastructure, can generate sufficient heat to ignite nearby flammable materials. Moreover, if a battery management system fails to regulate voltage properly, overcharging can occur, causing gas buildup within the cell and eventual rupture. Once ignited, lithium-ion fires are notoriously difficult to extinguish due to the chemical nature of the electrolyte and the ability of the fire to reignite even after apparent suppression.
The study places particular emphasis on the environmental context of underground garages, where structural and operational factors amplify the danger posed by EV fires. These facilities are typically constructed with reinforced concrete and feature limited natural ventilation, creating a semi-enclosed environment that traps heat and smoke. In the event of a fire, the accumulation of toxic gases—such as hydrogen fluoride, carbon monoxide, and various organic compounds released during battery decomposition—poses a serious threat to human health and complicates evacuation and firefighting efforts.
Furthermore, the spatial layout of underground parking areas exacerbates the risk of fire propagation. Vehicles are often parked in close proximity, sometimes with minimal clearance between bumpers and side panels. This high-density arrangement allows flames and radiant heat to easily transfer from one vehicle to another, potentially triggering a cascading ignition sequence. The presence of combustible materials—such as plastic trim, upholstery, tires, and stored maintenance supplies like oil, solvents, and spray paints—further fuels the fire. In mixed-use garages where both electric and internal combustion engine vehicles are parked, the risk is compounded: an EV battery fire can ignite the fuel tank of a neighboring gasoline-powered car, leading to secondary explosions and a rapid escalation of the incident.
Ventilation limitations represent another critical challenge. Unlike open-air environments where smoke and heat can dissipate naturally, underground garages rely heavily on mechanical ventilation systems. During a fire, these systems may become overwhelmed or fail altogether, especially if power is lost. Smoke stratification—the layering of hot, toxic gases near the ceiling—can obstruct visibility and disorient occupants attempting to evacuate. Firefighters entering the space face reduced situational awareness, increased inhalation risks, and difficulty in locating the seat of the fire. Additionally, the confined geometry of many underground parking structures restricts access for large fire apparatus, limiting the deployment of high-capacity water pumps and aerial ladders.
The paper also addresses the unique characteristics of EV fires themselves, distinguishing them from conventional vehicle fires. One of the most notable traits is their persistence. Lithium-ion battery fires can burn for hours, even days, due to the continuous release of energy from ongoing chemical reactions within the cells. Traditional firefighting methods, such as water spray or foam application, may suppress surface flames but often fail to cool the core of the battery pack sufficiently to prevent re-ignition. This phenomenon, known as “thermal rebound,” requires sustained cooling efforts and extended monitoring post-extinguishment.
Another distinguishing feature is the potential for delayed ignition. In some cases, a damaged battery may appear stable immediately after a crash or charging incident but enter thermal runaway minutes or even hours later. This latency complicates emergency response protocols, as first responders may mistakenly believe the danger has passed. The study underscores the need for prolonged on-scene observation and the use of thermal imaging cameras to detect residual heat pockets within the battery module.
Given these complexities, Deng Xiaojun outlines a series of evidence-based countermeasures designed to enhance fire safety in underground EV parking environments. The proposed strategies are structured around four key pillars: personal protection for emergency personnel, rapid situational assessment, clear operational procedures, and effective egress planning.
First, the importance of robust personal protective equipment (PPE) cannot be overstated. Firefighters responding to EV fires must be equipped with full structural firefighting gear, including heat-resistant turnout coats, self-contained breathing apparatus (SCBA), and chemical-resistant gloves and boots. Given the risk of exposure to hazardous fumes, respiratory protection is paramount. The study recommends integrating wearable physiological monitoring systems into standard PPE to track vital signs such as core body temperature and heart rate, enabling early detection of heat stress or toxic exposure. Regular training and live drills are essential to ensure proper donning and use of protective gear under high-stress conditions.
Second, rapid and accurate assessment of the fire scene is critical for effective intervention. The paper advocates for the deployment of advanced monitoring technologies, including high-sensitivity smoke detectors, thermal imaging drones, and real-time data integration platforms. Surveillance cameras already installed in most modern garages can provide immediate visual confirmation of fire location and intensity. When combined with vehicle registration databases and remote battery status systems, responders can quickly identify whether the involved vehicle is electric, determine its battery chemistry, and assess its state of charge—all of which influence tactical decisions. For example, a fully charged lithium-ion battery poses a greater risk than one at partial charge, necessitating more aggressive cooling measures.
Third, the study emphasizes the need for clearly defined operational protocols tailored to EV-specific incidents. This includes the immediate establishment of a safe perimeter, deployment of specialized firefighting teams trained in battery fire suppression, and activation of automatic fire suppression systems if available. The research highlights the effectiveness of targeted water application—not just to extinguish flames but to cool the battery pack to below its thermal runaway threshold, typically around 80–100°C. In some cases, submerging the battery in a water bath may be necessary, though this presents logistical challenges in underground settings. The use of fire-resistant containment barriers and temporary isolation zones can help prevent lateral fire spread while minimizing collateral damage.
The integration of unmanned aerial vehicles (UAVs) equipped with extinguishing agents is another innovative recommendation. Drones can access hard-to-reach areas, deliver suppressants with precision, and reduce the need for personnel to enter high-risk zones. Additionally, the coordination between fire services, traffic management, and building operators through a centralized command center ensures seamless information flow and resource allocation during emergencies.
Finally, the paper stresses the importance of well-designed evacuation routes and safety corridors. In underground garages, every second counts during an evacuation. Clear, unobstructed pathways marked with photoluminescent or reflective signage should be maintained at all times. Emergency lighting powered by backup generators must remain functional even during power outages. Multi-level egress systems, including stairwells, ramps, and interconnections with adjacent buildings, provide redundancy in case primary routes are blocked. Regular evacuation drills involving both facility staff and regular users can significantly improve response times and reduce panic during actual incidents.
Beyond immediate firefighting and evacuation, the research calls for a proactive approach to fire prevention through improved design standards, maintenance practices, and regulatory oversight. Charging stations should be equipped with overload protection, ground fault detection, and automatic shutoff mechanisms. Regular inspection and replacement of aging cables and connectors are essential to prevent electrical faults. Parking layouts should incorporate designated EV charging zones with adequate spacing between vehicles and proximity to fire suppression infrastructure. Building codes may need to be updated to reflect the evolving risks associated with electrified transportation.
The implications of this research extend beyond fire departments and building managers. Automakers, charging infrastructure providers, and policymakers all have a role to play in mitigating the risks identified in the study. Enhanced battery safety features—such as improved thermal management systems, flame-retardant enclosures, and real-time health monitoring—can reduce the likelihood of failure. Standardized communication protocols between vehicles and charging stations could enable early warning of anomalies. Regulatory bodies might consider mandating fire risk assessments for underground parking facilities with high EV penetration rates.
Public awareness is equally important. Many EV owners are unaware of the specific fire risks associated with their vehicles or the importance of proper charging practices. Educational campaigns promoting safe charging habits—such as avoiding overnight charging on degraded outlets, not using extension cords, and monitoring battery temperature—can go a long way in preventing incidents before they occur.
In conclusion, Deng Xiaojun’s research offers a timely and thorough examination of the fire safety challenges posed by the growing presence of electric vehicles in underground parking environments. By combining technical analysis with practical recommendations, the study provides a roadmap for enhancing preparedness, improving response capabilities, and ultimately safeguarding lives and property. As urban centers continue to embrace electric mobility, integrating these insights into building design, emergency planning, and public policy will be essential to ensuring a safe and sustainable transition.
Deng Xiaojun, Yacheng District Fire and Rescue Brigade, Sichuan Provincial Fire and Rescue Corps. Building Fire Protection, January 2024. DOI: 10.1234/bfp.2024.01.009