Podcast: GKN Aerospace Incident Offers Lessons in Reactive Hazard Management

A May 23 runaway reaction at GKN Aerospace's Garden Grove, California, facility forced 50,000 residents to evacuate after a cooling system failure allowed a tank of methyl methacrylate (MMA) to overheat and begin polymerizing. In this episode, Trish Kerin examines what went wrong, including a temperature gauge that couldn't read above 100 degrees, masking how hot the tank actually got. She discusses warning signs operators should watch for, such as small temperature trend shifts, and why critical instrumentation needs to feed into control systems rather than rely on manual checks. Kerin also applies her APTBED framework to identify gaps in tacit knowledge, procedures and bias that may have contributed to the incident.

Transcript

Welcome to "Process Safety with Trish and Traci," the podcast that aims to share insights from past incidents to help avoid future events. Please subscribe to this free, award-winning podcast on your favorite platform so you can continue learning with Trish and me in this series. I'm Traci Purdum, editor-in-chief of Chemical Processing, and joining me, as always, is Trish Kerin, director of Lead Like Kerin. Trish is also our Stay Safe columnist. Hey, Trish, how are you?

Trish: I'm great, Traci. How are you doing today?

Traci: I'm doing well, and I'm very interested in your thoughts on our episode today. We're going to tackle a recent incident involving a runaway reaction. Authorities suspect the cooling system responsible for maintaining the temperature of a tank filled with a hazardous chemical at GKN Aerospace failed, causing the runaway reaction that forced 50,000 people from their homes in Orange County, California, on May 23. GKN, based in Britain, makes landing gear, jet engines and other parts for commercial and military aircraft at its Garden Grove facility. While it's not a chemical facility, there's a lot we can learn from this incident. So, first, can you explain a little about what happened?

GKN Runaway Reaction — What Happened?

Trish: Yeah, so look, we're still trying to understand a lot about what happened. There's still a lot of information that's not available. What we do know is that there was a tank of MMA, and it started to have what's called a runaway reaction. That means the product in the tank started to heat up, and as it heated up, that additional heat generated more pressure in the tank, which generated more heat, which generated more pressure, which generated more heat. That's essentially what a runaway reaction does: One parameter goes outside its normal range, and suddenly it starts to snowball, building and building and building.

What we do know is that the temperature in the tank started to rise, and at some point it reached 100 degrees Fahrenheit. What we don't know is whether it exceeded 100 degrees, because the gauge on the tank only went up to 100. So it's possible the product in the tank went well beyond that, but we don't know for a fact, because there was no measurement available.

Now, it's important to know that this particular substance, MMA, should be kept below 95 degrees Fahrenheit. Above 95 degrees, it starts to polymerize and react. So we do know a reaction was taking place — we saw that with the heat. There were images showing the tank slightly bulging, and we know fire crews were spraying water constantly on the tank to try to cool it. One challenge with that approach is they can cool the outside, but they can't get the water spray to the inside.

So you can end up with the outside cooling down a bit and acting almost like a shell, a tank wall, while the reaction continues in the middle. That was, I think, the biggest concern for the responding authorities at the time — they didn't actually know what was going on inside that tank, and they didn't know if it was going to explode at any point. That would have released a lot of toxic vapors into the air, which is why there was such a widespread evacuation ordered around the vicinity of the plant.

Traci: You mentioned the temperature gauge didn't go above 100 degrees. Is that normal?

Trish: Look, I'd say it's not great design. Is it normal? I think there are probably a lot of situations out there where we don't have temperature gauges covering the range they should. One of the challenges with gauges — temperature, pressure or otherwise — is that the manufacturer pretty much guarantees accuracy within a certain range, say between 50 and 100 degrees. That's why they only show up to 100 degrees and down to 50. When you get gauges with very large ranges, they're not necessarily as accurate, which is why we don't tend to see them.

What I would have liked to see from a design perspective is perhaps an independent temperature gauge ranging from, say, 90 to 150 degrees — accurate, but not your normal gauge. Your normal gauge might run from 50 to 100. It's about making sure you have the right instrumentation working in the right ranges. Even in the kitchen, if you're making candy, you'll use a very specific temperature gauge, one quite different from a gauge used for cooking meat. That's exactly what we're talking about here: You don't get accuracy across huge temperature ranges, so you need specific gauges for specific applications.

Warning Signs

Traci: Interesting. Thinking about this, can we talk a little about the warning signs that might have gone unrecognized before this happened, and maybe touch on other ways to monitor this type of reactive-hazard escalation beyond having different gauges?

Trish: Yeah, so in this situation, I would have expected to see a trend change in the tank's temperature. The tank temperature should be relatively stable — it shouldn't change much at all. What I'd expect as a warning sign is a slight shift in temperature. For argument's sake, say it had consistently been sitting at about 80 degrees. If it's suddenly at 82, that's not a lot — only 2 degrees — but it's different. That's one of the classic weak signals I talk about: Just because something is still within its specification doesn't mean it's still normal. It might be changing trend in some way.

So I'd expect to see at least a slight increase in temperature over time, and to continue seeing that temperature climb. It's unlikely the reaction happened so quickly that nobody noticed it jump from 80 to 100 instantly — it wouldn't happen like that. There would have been an opportunity to see a trend. Now, the interesting thing is, if it's a manual temperature gauge — and I don't know if it was — and someone has to go out and look at it, you're not going to see the trend, because you'll only get a reading when someone checks it. For critical equipment, such as a temperature gauge on a temperature-sensitive product, you need that wired into your control system so you have trending data. Then you can go back and say, "We've seen a step change, we're seeing an increase, we need to respond now."

The interesting thing is, there would also be pressure gauges on the tank, because of the risk of a runaway reaction. There's also the ability to inject a chemical into the MMA that would stop the reaction. But when they tried to do that, they couldn't get the chemical injected because they believe the MMA had polymerized and blocked the injection point. At lower temperatures, when they first saw a trend change, it likely wouldn't have polymerized yet.

It comes down to how quickly you respond. Do they think, "No, we can still control this, so we won't inject the chemical," because that would ruin the batch? You'd have to dispose of the product if you did that. But it would have prevented the runaway reaction from kicking off and continuing as it did. So it's interesting to understand what information they had around that scenario, and at what point they decided whether to inject the chemical early — say, around 95 degrees — versus waiting until 100 degrees, when it might have polymerized and they couldn't get the chemical in.

Creeping Change

Traci: We've talked about the normalization of deviation in many contexts. GKN had prior OSHA and air-quality violations. How do recurring low-level compliance failures create the conditions for a catastrophic reactive-hazard event?

Trish: That's a really interesting question. I think the challenge is that if we're seeing recurring compliance issues, even at low levels, that tells us something about operational discipline — about whether the company is focused on managing the important details. It's not a definite predictor of an incident; there are no definite predictors. We don't have that capability yet. But it does suggest: If we're constantly getting these low-level noncompliance issues, what are we missing as an organization?

So if you're in a facility and you have ongoing issues with the regulator over what seem like insignificant things, take a look at the important things. Are they being done as they should, on a regular basis, to the detail and level you need? Or are we also missing some of the big things? It's possible the small things really don't matter. But when we're missing the little things, it makes you wonder what's happening with the big ones. Look for that big trend rather than dismissing it as just a small detail in one part of the plant. Understand the big picture, because there could be a wider cultural issue — a wider normalization of deviance — where we're missing important indicators simply because no one's looked for them yet.

Keeping The Public Informed

Traci: Switching gears, emergency officials were using terms like "thermal runaway" and "BLEVE" during press conferences. How do you bridge the communication gap between technical hazard realities and the public's understanding, and who's responsible for making sure the public understands what we mean by those terms?

Trish: Yeah, so first, we often assume the public won't understand the technical details. So either we baffle them with jargon and don't bother explaining, or we don't tell the public anything at all. Both of those are mistakes. The public isn't stupid — they just don't have training in the specific terms we use. So it's up to industry and emergency responders to be transparent with the details and explain them in ways people can understand.

Earlier, I talked about thermal runaway — how heat generates pressure, and increased pressure generates more heat, and that generates more pressure, and so on. There are ways to explain that simply. It's almost like boiling a pot of water: You can boil it faster if you put the lid on. That's not exactly a thermal runaway, but it's similar — by increasing the pressure in the pot, the temperature rises faster, producing more steam, which produces more pressure, which produces more temperature. It's about taking an everyday example and explaining it in a way people can understand.

BLEVE is a bit more complicated. It stands for "boiling liquid expanding vapor explosion." Normally, we see BLEVEs involving liquefied petroleum gas, or LPG, tanks. Typically there's a fire impinging on, or touching, the outside of the tank, heating it from the outside. That causes a pressure increase inside the tank, which causes LPG vapor to release through the emergency valve, which causes the liquid level in the tank to drop.

The challenge with a BLEVE — and it's a similar situation here — is that instead of a fire hitting the tank from the outside, we had heat generated on the inside, causing vaporization and boil-off of the chemical, which means the liquid level decreases. But that liquid level provides a cooling effect on the tank wall. If the liquid drops while the heat continues, the steel starts to weaken. As steel heats up, it gets weaker and weaker, and eventually the pressure becomes too much. If the steel is weak enough, the pressure releases catastrophically and blows the tank apart — that's effectively what a BLEVE is. So we need to keep the steel as cool as possible to prevent that weakening so it can continue to hold the pressure. I think that's a fairly reasonable way to explain a BLEVE to the public.

When we think about these things, it's about using everyday terms people understand. We're talking about making sure the tank doesn't catastrophically fail — that it doesn't blow a hole in itself. We don't want to use inflammatory language like "it's going to explode and pieces will go everywhere." That's not helpful; it just makes people nervous and doesn't communicate the risk effectively. It's about using simple terms, and visuals are really helpful, too, especially in press conferences. We can produce animations that explain things clearly and simply.

The U.S. Chemical Safety Board has been doing this for years. So if we have a press conference and need to explain something complex, can we produce a graphic or animation that shows and explains it in ways people can understand? It's about simplifying the language and tying it back to everyday experiences.

Traci: That reminds me of the podcast we recently did on O-rings, demonstrating on TV, very simply, what happens to an O-ring at frigid temperatures. So yes, having that clear, concise, easy-to-understand approach is important.

Trish: Yeah.

APTBED — Framework For Prevention

Traci: Now I want to apply some of the lessons you've shared in the past using the APTBED framework you discussed in a recent episode — authority, psychological safety, tacit and explicit knowledge, biases, expectations, and documented decisions. Where do you think the GKN situation most likely broke down, and what would a facility need to have genuinely in place to prevent this class of reactive-hazard incident?

Trish: Yeah, so, as I said, without knowing the full details — we saw emergency response come in and take over, which is what happens in an emergency. So I think authority was pretty clear; the emergency services were in charge. It's hard to say where psychological safety sits without more background on the organization, so I can't really comment on that.

But I think some of the key challenges were around tacit and explicit knowledge. Tacit knowledge is the experience people have — what do they know, what's their experience telling them about managing this particular product? Did they have experienced people who recognized early enough that something was starting to go wrong? Was there a gap in tacit knowledge? As for explicit knowledge, did their procedures tell them precisely what to do in this scenario? I'd expect there to be clear procedures for dealing with a potential thermal runaway of MMA at a facility that stores it — that's an easily foreseeable situation.

They mentioned their cooling system stopped and they didn't know why. That's an important thing to understand. What are the procedures around that cooling system? What's the maintenance program? How did it stop working without anyone knowing why? That sounds like it could be a critical safety system if it's what keeps the MMA at an appropriate temperature so it doesn't thermally run away.

I also think bias likely played a role — an illusion of control. "No, no, we know what we're doing. We've got this under control. We manage these tanks all the time." When, in fact, they weren't in control. Expectations probably played a part, too, including how clearly those expectations were communicated to the community — the residents who had to evacuate. What were they told about what was needed and expected so they could prepare adequately?

So I think those were the three key areas. I don't think there was necessarily an issue with documenting decisions, at least not that's apparent at this point. But really it's about knowledge — what biases are leading people not to apply their knowledge correctly — and how we're managing expectations.

I'd expect to see detailed emergency-response processes for this kind of event, and detailed plant procedures covering what to do if you notice a change in temperature trend, what to do if the cooling system isn't working efficiently or isn't working at all, and troubleshooting guides — not quite emergency procedures, but guidance on what to focus on and work on if certain conditions arise.

That's what I'd expect to see at a facility handling a substance like this. In my background, I worked at a PVC manufacturing facility. PVC uses a chemical called vinyl chloride monomer, which is polymerized to become polyvinyl chloride, or PVC. That monomer can also have runaway reactions. We had very specific troubleshooting guides for what to do if we thought we had a runaway reaction — how to manage it, what chemicals to inject to stop it, and what cooling systems were available to prevent the reaction from starting in the first place. Those guides were really important tools to help people troubleshoot through the challenges.

Traci: Trish, is there anything you want to add?

Trish: I think one thing I mentioned earlier is that if you're seeing low-level violations at your facility, go look at the important systems. Don't assume they're working just because they're important. What's your maintenance program doing? How are you managing the integrity of your safety-critical systems? How do you know they're working to prevent an incident? And how do you know your response systems will work to mitigate an incident if one happens? Take a deep look at what you're doing at your own facility. Make sure you understand it, and make sure you have systems in place to manage the key hazards. MMA was a key hazardous substance at this facility — make sure you have the right systems in place to manage the processes and hazards you have.

Webinar Information

Traci: Well, Trish, thank you for helping us understand the big picture and the importance of managing the integrity of our systems. Before we wrap up, I want to let listeners who'll be tuning in over the next week or so know that you have a webinar coming up [June 30, 2026 at 9:00 AEST (June 29, 6:00 p.m. CDT)] they might want to attend. Want to tell us a little about that?

Trish: Yeah, I'm doing a webinar focused on leadership in uncertain times — looking at key strategies and tools we can use to navigate some of the challenges we're all facing globally right now. We're certainly operating in uncertain times, and we need to focus on specific elements of leadership to get the best outcomes. You mentioned APTBED — I go through that framework in the webinar and provide a number of resources and tools people can take away to help them remember these key strategies for more effective safety leadership in these difficult times.

Traci: It's going to be a great webinar. And I understand you're still offering the CP reader discount for us? [Register here: https://square.link/u/flP19IZX and use code: CPREADER for a $5 discount]

Trish: Yes, I am.

Traci: Trish, once again, thank you for helping us understand this recent event. Unfortunate events happen all over the world, and we'll be here to discuss and learn from them. Subscribe to this free podcast so you can stay on top of best practices. You can also visit us at ChemicalProcessing.com for more tools and resources to help you run efficient and safe facilities. On behalf of Trish, I'm Traci, and this is "Process Safety with Trish and Traci." Thanks again, Trish.

Trish: Stay safe.