Experiments Studying Fire Blanket Effectiveness to Control Electric Vehicle Fires are Completed

Researchers from the Fire Safety Research Institute (FSRI), part of UL Research Institutes, continued work on the Fire Safety of Batteries and Electric Vehicles research project. In this third phase of experiments, researchers simulated two electric vehicle (EV) fire scenarios: one in which a fire blanket is deployed with no water suppression (e.g., where water is not available, or well in advance of water suppression) and another in which the blanket is deployed with initial and ongoing water suppression. 

Exploring Multiple EV Fire Scenarios

Following a review of U.S. and international standard operating procedures with guidance from the project’s technical panel, researchers designed experiments evaluating the two most common ways the fire service deploys a fire blanket during an EV fire incident. One experiment set focused on using a fire blanket to control the EV fire without water suppression. The other experiment set focused on the use of a fire blanket in combination with water suppression using an under-car type EV nozzle to control the fire. 

These experiments will answer critical research questions:

• Are fire blankets effective at controlling an EV fire until water arrives?
• Can fire blankets slow or stop thermal runaway propagation when the battery pack is involved?
• Does suppressing the cabin fire before blanket deployment improve blanket effectiveness?
• How does water suppression combined with blanket deployment impact thermal runaway propagation?
• When should fire blankets be removed?
• What is the post-deployment condition of fire blankets?

EV Fire Blanket Experiment Setup and Data Collection

Researchers completed a total of four (4) tests using two (2) EV models, selected based on their performance in previous water suppression experiments that evaluated hose stream effectiveness. Each scenario was tested one time on both EV models. Before the experiments, each EV battery pack was charged to 100% to induce a severe thermal runaway propagation behavior. Researchers placed a premixed burner below the lithium-ion battery pack to apply a consistent heat source and induce a thermal failure in the battery cells. This burner remained in operation until the battery pack heated enough to trigger thermal runaway propagation. After propagating thermal runaway was confirmed, six (6) minutes were allowed to pass to simulate a standard fire department response time. After six (6) minutes the fire blanket was deployed and left in place until experiment termination, while temperature, flame spread, gas species, and blanket condition were monitored. The same procedure was followed for the fire blanket with water suppression tests; however, this time, researchers positioned an EV nozzle below the vehicle when the fire blanket was deployed. Again, temperature, flame spread, gas species, and blanket condition were monitored until experiment termination.

Similar to previous experiments, fire measurement instrumentation was used to collect data on heat flux, fire behavior, gas species, and occupational and environmental exposure hazards. This data will inform researchers’ analysis of fire blanket effectiveness in controlling thermal runaway, suppressing the vehicle fire, and reducing heat and smoke exposure to first responders.

• Heat flux gauges were placed 9 feet from the vehicle to measure thermal exposures to nearby first responders, vehicles, or structures.
• Thermal imaging cameras were employed to monitor thermal runaway, battery pack temperatures, and flame spread while the fire blanket was in place.
• Fourier-transform infrared spectroscopy (FTIR), gas chromatography, sorbent tubes, and passive silicone samplers were utilized to enable measurement of gas, vapor, and particulate emissions around the vehicle and in the fire plume, with partners at the National Institute for Occupational Safety and Health (NIOSH) and Duke University.
• PPE swatches were positioned at key locations approximately 15 feet from the vehicles, with additional swatches and air sampling equipment attached to firefighters conducting fire blanket deployment and other suppression activities. This setup enabled further analysis of potential occupational exposure hazards as part of the Emerging Issues Related to Personal Protective Equipment research project.
• Vehicles were parked on a metal pan platform designed to collect suppression water runoff for analysis of chemical contamination.
• Prior to experiments, research partners from Munro & Associates installed thermocouples into the vehicle battery directly onto battery modules to measure temperature during the experiment. They safely removed, opened, and analyzed battery pack conditions post-test, following a similar process to that which was used in the water suppression experiments. 

These experiments, as well as experiments conducted by the Fire Protection Research Foundation, demonstrated a potential explosion hazard when fire blankets are used during electric vehicle (EV) fire suppression efforts when there is battery involvement. The experiments reinforce the need for continued research on EV firefighting tactics.

Evaluating the Effectiveness of Water Suppression with Foam Additive on an EV Fire

One (1) additional experiment was conducted to evaluate water suppression with a foam additive on an EV fire. This test was conducted with the same instrumentation as the water suppression experiments from the prior research phase, with additional instrumentation to measure foam concentrate flow rate during the experiment. The premixed burner below the vehicle remained in operation until researchers confirmed thermal runaway propagation in the lithium-ion battery pack. The fire was allowed to develop for the same six (6) minutes to simulate typical fire service response time. Then, manual water suppression with a foam additive was initiated. After ten (10) minutes of on-scene time, researchers used a lift to tilt the EV and improve battery pack access for water suppression. The vehicle remained in this position and monitored for additional gas release or thermal energy generation activity.

“A key component of this research is to evaluate how effective traditional firefighting tools can be at controlling and extinguishing EV fires. An important step to develop this evaluation process includes a thorough review of current firefighting operations, with the help of our technical panel. We do all this work with the goal of developing tactical considerations to help the fire service make better, safer decisions on the fireground.”
—Adam Barowy, lead research engineer, FSRI

Preparation to Release Findings Related to EV Fires

Data analysis will continue and inform future tactical considerations. Researchers are currently working on a technical report that will include operational recommendations for fire departments to be released later this year. Analysis of exposure hazards will support future publications in the Emerging Issues Related to Personal Protective Equipment research project.