A 7,000-gallon tank of methyl methacrylate (MMA) at a Garden Grove aerospace plant is now in a “crisis situation,” with officials warning it could explode or rupture within hours, forcing the evacuation of 40,000 residents across six Orange County cities. The evacuation zone spans multiple blocks in Garden Grove, Cypress, Stanton, Anaheim, Buena Park, and Westminster, with shelters open at three locations as first responders race to cool the tank before it reaches a critical temperature threshold.
Why This Chemical Is So Dangerous—and Why Officials Are Racing Against Time
The tank contains methyl methacrylate (MMA), a flammable liquid monomer used in plastics manufacturing. While the polymerized form of MMA is harmless, the liquid version is toxic at high concentrations and can cause respiratory issues or chemical burns. But the real danger lies in its chemical behavior: when heated, MMA undergoes a process called thermal runaway, where the reaction generates more heat than it absorbs, spiraling out of control. “It’s durable, lightweight, transparent, so it could even be used as a substitute for glass,” said Elias Picazo, assistant professor of chemistry at USC, describing the final product—but the liquid form inside the tank is far more volatile.
As of Friday afternoon, firefighters had lowered the tank’s temperature to 61 degrees Fahrenheit, with 50 degrees the target before attempting any intervention. But the risk of a BLEVE—a boiling liquid expanding vapor explosion—remains imminent if the tank’s pressure or heat exceeds safe limits. “We know the tank is going into thermal runaway, and we’re going to pull everybody out of the area, make sure it’s safe, and let the tank do what it’s going to do,” Craig Covey, an Orange County Fire Authority division chief, told reporters. The explosion itself would release toxic fumes and shrapnel, creating a secondary hazard zone.
“The other hazard is the explosion itself. And it sounds like it’s already the reaction has already initiated, and that’s where the worry comes in for the explosion.”
Thermal runaway in MMA is particularly treacherous because the reaction is self-sustaining. “You have a reaction that is initiated by heat, but it also releases heat as it goes on, that then leads to the runaway, where it’s uncontrollable,” Picazo explained. “And this is a very large-scale reaction that produces a lot of heat very quickly.” The tank’s bulging Thursday night—captured in aerial footage—signaled the pressure buildup had already begun, a clear warning that containment was failing.
Evacuation Chaos: How 40,000 Residents Were Forced Out in Less Than 24 Hours
The evacuation order, issued Thursday evening, initially covered a smaller area but expanded dramatically by Friday, swallowing entire neighborhoods. The zone now stretches north of Trask Avenue, south of Ball Road, east of Valley View Street, and west of Dale Street—an area that includes parts of West Anaheim and Cypress. Officials with the Garden Grove Police Department reported a 15% refusal rate among residents, with some choosing to stay despite door-to-door warnings. “It’s a crisis situation,” Covey said, emphasizing the urgency.
Three evacuation centers were established to accommodate displaced residents: the Garden Grove Sports and Recreation Center, the Cypress Recreation and Community Center, and—added late Friday—Savannah High School in Anaheim. The Orange County Fire Authority urged residents to avoid calling with non-essential questions, redirecting them to a 24-hour hotline (714-741-5444) to keep emergency lines clear. Meanwhile, the 22 Freeway remained open, though traffic was disrupted as evacuees fled with little more than essentials.
“We came back, and half the cars are gone and the other half are leaving all at once.”
Loo, who lives about two miles from the plant, reported headaches and dizziness after returning home around 3 a.m. Friday, suggesting low-level exposure to fumes. His experience mirrors that of Jude Thomas, who had lived near the GKN Aerospace plant for six years without concern—until Thursday. “Everything will change, for sure, once this is done,” Thomas said. “We will think about moving out from there.” The psychological toll of the evacuation is already visible: families sleeping in plastic chairs at shelters, children clinging to parents, and residents glued to their phones for updates.
The Plant at the Center of the Crisis: GKN Aerospace’s MMA Tank
The leaking tank is located at the GKN Aerospace facility in Garden Grove, a manufacturer of aerospace components. The plant uses MMA—a key ingredient in acrylic plastics—as part of its production process. While the exact cause of the temperature spike remains under investigation, experts say such incidents are rare but not unheard of in industrial settings. “It’s something that should not have happened,” Covey said, hinting at potential equipment failure or procedural oversight.
GKN Aerospace has not issued a public statement on the incident, leaving details about the tank’s maintenance, inspection records, or prior warnings unclear. California’s evacuation orders are triggered only by “immediate threats to life,” a threshold that officials confirmed had been met. The plant’s proximity to residential areas—some homes sit within a half-mile of the facility—has amplified the crisis, turning a potential industrial hazard into a full-scale community emergency.
What Comes Next: The Race to Cool the Tank—and the Uncertain Timeline
As of Saturday morning, firefighters are focusing on stabilizing the tank’s temperature, a process that could take hours—or fail entirely. If the tank reaches thermal runaway, the only option may be to evacuate a larger area and let the explosion occur in a controlled manner. “If you build too much heat or pressure, then you get the explosion,” Picazo warned. The EPA and FEMA have been briefed on the situation, with state officials coordinating with local authorities. Rep. Derek Tran (D-Westminster) urged residents to follow guidance from emergency officials, adding that his office is “in close contact with local police, fire, and emergency response officials.”
“My office is in close contact with local police, fire, and emergency response officials as they work to contain the hazardous materials, assess air quality, and ensure residents and first responders are safe.”
—Rep.
Gov. Gavin Newsom’s office confirmed he had been briefed on the leak, with the state’s Office of Emergency Services coordinating with federal agencies. However, no timeline has been provided for when residents can safely return. The uncertainty is compounded by the fact that MMA’s vapor can linger in the air for days, requiring extensive air quality testing before areas are declared safe. In the meantime, officials are advising residents to avoid the impacted zones and monitor updates from local authorities.
The longer-term implications extend beyond immediate safety. The evacuation has disrupted businesses, schools, and daily life for tens of thousands. Some residents, like Thomas, are already considering permanent relocation. Others may face financial losses from damaged property or lost wages. The incident also raises questions about industrial safety regulations in Orange County, particularly for facilities handling hazardous materials near populated areas.
The Human Cost: Stories from the Evacuation Zone
At the Cypress Community Center, families waited in the parking lot Friday night, some with only the clothes on their backs. Jude Thomas’s son had warned him for years about living so close to the plant, but Thomas dismissed the concerns—until Thursday. Now, he’s packing boxes, unsure if he’ll return. “We will think about moving out from there,” he said. For others, like Miguel Loo, the evacuation was a chaotic scramble: grabbing medications, pet supplies, and important documents while battling headaches from potential fume exposure.
The emotional toll is evident in the stories of evacuees. Victor Romero carried his two-year-old daughter on his shoulders as he waited for updates, his face etched with worry. “We’re trying to evacuate, and I’m getting dizzy with a headache in the middle of it,” Loo said. The uncertainty—how long the evacuation will last, whether their homes are safe—hangs over every conversation. For many, this is their first experience with a large-scale chemical emergency, and the lack of clear answers is deepening the anxiety.
What Happens If the Tank Explodes?
If the MMA tank reaches thermal runaway, the explosion could release toxic fumes, shrapnel, and a fireball with a radius of hundreds of feet. The immediate danger would be to first responders and nearby structures, but wind patterns could carry fumes into residential areas. “The other hazard is the explosion itself,” Picazo said. “And it sounds like the reaction has already initiated.” Officials are preparing for the worst-case scenario: a controlled detonation to minimize collateral damage.
Historically, similar incidents—like the 2019 MMA explosion in Texas—have resulted in multi-block evacuations and long-term air quality concerns. In Garden Grove, the proximity to freeways and dense housing means any explosion would have far-reaching consequences. Residents are being advised to stay away from the area until further notice, with no clear timeline for when they can return.
The crisis also highlights the risks of storing large quantities of hazardous materials near urban areas. While industrial accidents are rare, when they occur, the stakes are high. For now, the focus remains on cooling the tank—and praying it doesn’t reach the point of no return.
For updates, residents are directed to the Orange County Fire Authority’s hotline (714-628-7085) or the 24-hour call center (714-741-5444). The situation remains fluid, with officials urging patience and caution as they work to resolve the crisis.
