Lithium-ion batteries are the newest of our myriad evolving hazards to capture the attention of the fire service. These batteries are increasingly being used in a range of products including electrical vehicles and as supplemental energy facilities in the form of photovoltaic installations in buildings.
The research on these types of fires clearly highlights the significant changes in firefighting hazards presented – hazards that dictate new approaches to suppression. Additional questions and investigation are now being directed at the contamination hazards that may be created by these unique fires. Here we attempt to answer several of these questions related to potential contamination hazards and the impact on firefighter protective clothing, particularly, if these forms of contamination warrant specialized gear cleaning.
What types of contamination do Li-ion battery fires produce?
Several studies have sought to address the decomposition products emanating from Li-ion battery-based fires, often with a focus on electric vehicles (EVs). These studies [1-3] have shown a wide range of contaminants, where some produced chemicals that differ from conventional structural fire contaminants. For example, fire smoke evaluated for the presence of chemicals shows hydrogen fluoride, hydrogen cyanide, hydrogen chloride and sulfur dioxide, as well as various fluorinated phosphorus and lithium-based compounds. In addition, the runoff from such fires includes elevated levels of lithium, not unsurprisingly, with heavy metals that include nickel, manganese and cobalt. Yet, these same studies have shown the generation of various volatile and semi-volatile organic compounds, including polynuclear aromatic hydrocarbons (PAHs), which are typical of nearly all fires.
Let’s turn to Li-ion battery fires in structures. Any structural fire will create a unique set of contaminants based on the nature of the burning contents and their composition. Structural fires will vary in the generated levels of specific contaminants depending on the fireground conditions and many factors. Thus, there will be some of the same contaminants commonly found in the average structural fire as well as some novel chemicals that are less common, particularly those originating from the lithium, phosphorous, cobalt and fluorine-based contents.
What are the hazards of Li-ion battery fire contaminants?
Given the wide range of potential chemicals, there is an equally wide span of chemical hazards in terms of their toxicity, reactivity and flammability – hazards that can pose both short- and long-term effects. Some of these chemicals are well characterized in terms of exposure hazards that can include acceptable inhalation concentration levels, and in some cases, threshold levels for skin contact, but many are not.
In examining some potentially relevant chemicals, some idea of specific hazards can be inferred. For example, hydrogen fluoride, which is a uniquely dangerous, strong inorganic acid has been found in smoke for Li-ion battery fires at levels approaching 600 ppm. As a frame of reference, the immediately dangerous to life and health (IDLH) concentration for hydrogen fluoride is only 30 ppm. Furthermore, cobalt is a dangerous heavy metal that is most likely to show up in a form combined with other atoms as an inorganic chemical. Fumes of these chemicals are considered dangerous at relatively low levels in air (NIOSH Recommended Exposure Limit of 0.05 milligram per cubic meter over an 8-hour exposure [4]). What is of greatest interest for this discussion is understanding which contaminants remain on PPE and the expected residual concentrations following the fire event.
How well are Li-ion battery fire contaminants removed through PPE cleaning?
Before we answer this question, let us first reinforce our baseline cleaning practices. Conventional cleaning entails the use of a programmable washer/extractor with a specialized formulation for washing with a suitable detergent and multiple rinses. In many cases, this approach is considered appropriate for a wide range of structural fires, even where the contamination can be highly varied. It is recognized that this approach to laundering gear does not fully remove all contaminants; some contaminants may be completely removed while others only partially, depending on specific chemicals. However, these practices are in place for how most firefighter protective garments are currently cleaned.
Now, to directly answer this question, an appropriate methodology would be needed to determine how effective any cleaning process would be in removing the contaminants that are uniquely associated with Li-ion battery fires. Though it is possible to simply analyze gear that has been subjected to such a fire, this approach does not always yield valid answers because it is impossible to directly compare contamination levels before and after cleaning on the same sample, as destructive analytical techniques are often required, which can either be done before or after the cleaning, but not for both conditions. Any attempt to use wipe sampling will only pick up surface contamination and does not fully evaluate the extent of contamination that may have penetrated the outer shell material and other layers of the garment. Thus, the only way to determine the effectiveness of cleaning is to have knowledge of the precise level of contamination in a sample that is then subjected to cleaning.
In the case of Li-ion battery fire decomposition products, the suitable approach is to place specific known concentrations of relevant chemicals onto material samples and then analyze those same samples for remaining chemical levels following washing. This permits the calculation of contamination-removal efficiency and reflects the exact same approach that is used in NFPA 1851 for verifying the effectiveness of cleaning by independent service providers (ISPs) and other organizations.
At this time, we are only aware of a few efforts where this approach has been attempted in order to make claims of decontamination effectiveness for the removal of Li-ion battery decomposition products from turnout gear for specific cleaning processes. We caution that unless an approach is used exactly as described above, results should be approached with skepticism. To make matters more complex, there are no judged “safe” levels for most contaminants found in turnout clothing materials following a fire exposure. The exception could be acceptable restricted substance levels dictated in the OEKO-TEX 100 Standard for apparel such as those applied to heavy metals like cobalt, manganese and nickel, but these criteria are principally applied to clothing in a newly manufactured condition, not after it has been contaminated. Furthermore, use of airborne occupational exposure levels, such as OSHA or individual state permissible exposure levels (PELs), is not a reliable way for determining whether protective clothing can remain in service or whether it should be retired in the interest of safety. Finally, odor of the gear is never an adequate technique for judging the cleanliness of gear because not all substances have odor threshold concentrations that are at a meaningful level, and some contaminants are simply not volatile.
A more relevant measure is the actual concentration in the clothing material, as that amount of chemical could represent the total potential dose occurring from direct skin contact. This is because skin absorption can be a significant firefighter exposure pathway for some chemicals that can occur in the period following the gear’s exposure at the fire scene.
Is NFPA 1851 cleaning verification of an ISP relevant here?
We suspect that current cleaning verification procedures in NFPA 1851 could temporarily be a reasonable surrogate for understanding contamination removal for gear from Li-ion battery fires because the current specified chemicals cover a range of inorganic and organic chemical contaminants that have varying levels of solubility and volatility. For example, one heavy metal known to emanate from a Li-ion battery fire is cobalt, which is included in the test set for NFPA 1851 cleaning verification. Much of the other contamination that comes from Li-ion battery fires where adjacent materials to the batteries are involved in the combustion process are also reasonably represented by other chemicals. Nevertheless, research is still needed to at least demonstrate that this hypothesis holds true.
To this end, the Fire Protection Research Foundation and some other organizations are pursuing efforts to specifically study how well various selected Li-ion battery fire contaminants are removed from turnout clothing materials. In fact, consideration is being given to implementing optional standardized procedures for cleaning verification that specifically pertain to cleaning verification for relevant Li-ion battery fire contaminants in the upcoming edition of NFPA 1851.
Are there other potential effects of Li-ion battery fire contamination of turnout clothing?
Preliminary investigative efforts conducted by the Fire Protection Research Foundation and published in 2013 showed that turnout clothing was appropriate for Li-ion battery fires. This does not mean that there may not be certain effects of degradation that occur as the result of exposure to these fires. Several contaminants entail strong inorganic acids that may cause damage to materials. For example, hydrogen fluoride will be picked up in the moistened state of turnout clothing materials and then become hydrofluoric acid. This acid could be capable of damaging certain materials and components, though most fabric suppliers report their materials are unlikely to be degraded by such acids except under extraordinary conditions usually equated to long duration exposures at high concentrations.
The prudent practice is to undertake preliminary exposure reduction at the fire scene following exposure during a Li-ion battery fire as well with any structural fire and then isolate and bag the clothing followed by advanced cleaning. Specialized cleaning involving a presoak or other additional treatment or wash conditions such as additional rinses could also be applied to help avoid any long-term effects on the clothing (as well as help with the removal of contamination). However, until cleaning verification studies are coupled with an assessment of impact from the chemical exposure, no definitive statements can be made on which cleaning approaches are most effective.
What are the current recommendations related to gear following Li-ion battery fire exposure?
Bottom line: Firefighter protective clothing should be properly worn as part of an overall ensemble that is then subject to at least ordinary advanced cleaning after exposure to any Li-ion battery fire. Special precautions should be taken for the handling and isolation of the gear, particularly with the application of preliminary exposure reduction, with immediate follow-up of advanced cleaning.
It is possible that new information may be discovered that results in new best practices for protective clothing involved in Li-ion battery fires, but the procedures indicated above should cover most situations. As with any form of contamination, where concerns exist, firefighters should err on the side of caution and let knowledgeable authorities make decisions about the continued safety of your gear.
Note: The views of the author do not necessarily reflect those of the sponsor.
References
1. Johnsplass, J., Henriksen, M., Vågsæther, K., et al. (2017). Simulation of burning velocities in gases vented from thermal run-a-way lithium ion batteries.
2. Hynynen, J., Willstrand, O., Blomqvist, P., et al (2023). Analysis of combustion gases from large-scale electric vehicle fire tests. Fire Safety Journal, 139.
3. Szmytke, E., Brzezińska, D., Machnowski, W., et al. (2022). Firefighters’ Clothing Contamination in Fires of Electric Vehicle Batteries and Photovoltaic Modules—Literature Review and Pilot Tests Results. International Journal of Environmental Research and Public Health, 19(19), 12442.
4. NIOSH (1994). Cobalt metal dust and fume (as CO).
