Four Tips to Prepare for Energy Storage System Incidents

Peoria Fire-Medical Department - ESS Fire

Photo Credit: Peoria Fire-Medical Department

Futurists often say that if you want to know what tomorrow will bring, look at what’s happening on the fringes today. Massive energy storage systems, also known as electric energy storage, are not what we think of as the bread-and-butter hazmat call — like, say, a leaking tanker would be. Yet, that very well could be what hazmat teams will need to train for most in the coming years.

And with good reason. These systems, or ESSs, are popping up all over, are potentially deadly and are being built with limited understanding of what to do when things go wrong.

ESS is essentially any system that can store energy for later use. The United States built its first ESS facility in 1929 and got serious about the technology during the 1970s’ oil crisis. Today, the push for renewable energy and the development of lithium-ion batteries catapulted the drive for more ESSs. Currently there are about 600 facilities in the U.S. We can expect that number to grow. We can expect it to grow beyond the massive sites storing energy from solar or wind farms in the deserts. We can expect to see smaller ESSs in urban areas, probably on rooftops.

In its special report “Learning from Surprise”, NFPA did an outstanding job of detailing exactly what can go wrong for hazmat and fire responders. In April 2019 in Surprise, Arizona four firefighters were badly hurt when a lithium-ion ESS exploded. That explosion was preceded by what’s known as thermal runaway where the batteries rapidly discharged. That runaway increases heat and can lead to fire if unchecked. It also produces a cocktail of nasty gases.

NFPA wrote that the available research at the time revealed the gases released during thermal runaway are a highly flammable mix of hydrogen, ethylene, methane, carbon monoxide and others. Add to this, the site used a clean-agent gas system to make the area inhospitable for fire, but didn’t cool the temperatures. In addition to the batteries off gassing, the site’s fire system dumped more than 700 pounds of the gas Novec 1230.

When the hazmat team made entry, the increased oxygen and the existing heat and gas mixture lit off an explosion that sent flames as high as 20 feet and as wide as 75 feet.

UL did an extensive report on the incident, as did the Arizona Public Service. UL’s Stephen Kerber, who co-authored its report, told NFPA, “Even if we are able to safely ventilate it, where do those gases go, and are we creating secondary hazards because of where they go? I think that’s going to be a major challenge.”

Again, this isn’t just a middle-of-nowhere threat. In April 2021 a lithium-ion phosphate ESS housed on a shopping mall rooftop in Beijing caught fire with an explosion that killed two Beijing firefighters. According to PV Magazine, this facility was touted as the world’s largest user-facing ESS, the biggest electric vehicle charging station in the city, and the region’s first direct-current incremental grid set up.

If you don’t already have an ESS in your hazmat team’s jurisdiction, there’s a very good chance someone out there is working on plans to bring one in. So, what can be done?

As NFPA points out, there wasn’t much known about ESS safety in 2019 when the Surprise firefighters were nearly killed. And to borrow a Covid-vaccine analogy; when it comes to ESS safety, we are building the plane while it’s in flight.

Here are four steps you can take to better protect your hazmat team.


Learn as much as you can about ESSs and lithium-ion batteries. One of the Surprise hazmat members injured was an expert in this technology and was still caught off guard. Learn and continue learning; this is a fast-evolving technology and field.


Get involved at the planning stage. According to NFPA, one of the key lessons from Surprise was to develop response plans and safety systems during the design and implementation phase of these ESS projects. NFPA reported that the emergency response plan did not convey that a large flammable gas hazard or cell-to-cell and module-to-module cascading thermal runaway was possible. “An up-to-date history of the measurements of gas composition and potentially the percent LEL inside the structure would have been the best information for the firefighters on scene, and undoubtedly would have changed their response and would have prevented the injuries,” Co-author of the UL report Mark McKinnon told NFPA Journal.


Push for code creation where needed and code enforcement where they exist. NFPA points to areas where its existing codes could have helped in Surprise and areas where codes need to adapt to this changing technology. Jim Biggins, the chair of the NFPA 855 technical committee, says, “We’re looking at providing additional guidance in NFPA 855 both for explosion venting and normal venting of the battery enclosures and battery rooms. It’s such a large volume of gas coming out of a single cell during thermal runaway, and I don’t think anybody fully understood that mechanism previously.”


Be wary of cure-all safety technology and one-stop training. This area will require careful research. New safety technology for hazmat and fire responders will need to be fully vetted. And training on best practices is sure to change often. “What happens a lot with new technology is there’s an expectation that the fire department immediately becomes an expert on how to mitigate a hazard that they respond to, and I don’t think that’s a fair expectation,” Kerber told NFPA. “There has to be research upfront, there have to be codes and standards in place, and sometimes the technology gets ahead of that. In this case, there was really no good guidance. There was no good training.”

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