As firefighters worked through the night at GKN Aerospace in Garden Grove, temperatures inside a damaged tank of methyl methacrylate rose from 77 degrees Celsius to 90 degrees Celsius by Saturday morning, raising fears of either a massive explosion or a catast
For the third day, the clock kept ticking inside the damaged tank at GKN Aerospace in Garden Grove.
By 10 a.m. Saturday. firefighters said temperatures inside the compromised tank holding an estimated 7. 000 liquid gallons of methyl methacrylate had climbed to 90 degrees Celsius—up from 77 degrees the day before. The rise mattered because the liquid’s boiling point is 101 degrees Celsius. and officials said the tank’s gauge can only detect temperatures up to 100 degrees.
The conditions have steadily worsened. with an internal sprinkler system and unmanned ground sprinklers helping stabilize temperatures around 90 degrees. according to Orange County Fire Authority division chief Craig Covey and hazardous materials program manager Nick Freeman. But even with round-the-clock efforts. Freeman said Saturday afternoon the two most likely outcomes remained stark: a massive explosion of the pressurized tank or a rupture releasing thousands of gallons of a highly toxic chemical.
“We have all of our folks, and you name it, working on what our other options could be,” Freeman said.
Gov. Gavin Newsom declared a state of emergency over the industrial accident by Saturday afternoon. after the failure at the aerospace and spacecraft manufacturer displaced 40. 000 people from an evacuation zone extending roughly a mile in all directions from the facility. The zone includes parts of Garden Grove, Cypress, Stanton, Anaheim, Buena Park and Westminster.
In a social media post. Newsom said the California Governor’s Office of Emergency Services was mobilized since Friday and that state agencies were supporting impacted communities to “protect public safety. and assist local officials as response efforts continue.” He urged residents to “continue to follow guidance from emergency officials.”.
Evacuees spent Saturday in four shelters in Fountain Valley, La Palma, Huntington Beach and Anaheim, waiting for updates as the tank’s temperature continued to dictate the pace of the response.
“We left our homes, our memories, everything,” said Nathalie, 45, an Anaheim resident who spent the night at an American Red Cross-run shelter in Fountain Valley with her 16-year-old son, who has epilepsy, autism and cerebral palsy. “Is it going to explode? And what will be the consequences for us?”
Firefighters said the emergency began when the tank’s internal cooling system failed on Thursday. Late Friday. they relied on drone-based thermometers to estimate the temperature inside the tank. which showed 61 degrees with 50 degrees being the goal. By Saturday. Covey said crews realized the drone could measure only the temperature on the outside of the tank. not the inside. After a crew was sent in overnight to manually read the temperature gauge, officials found the interior temperature had risen.
Covey described the overnight correction as a decision with immediate risk. “We made a call last night to go back on the offensive,” he said. “We did put people in harm’s way last night.”
Inside the tank is an estimated 7. 000 gallons of methyl methacrylate. or MMA—a durable. lightweight and transparent polymer used in household goods or as a glass substitute. Officials said the polymer itself isn’t toxic. but the liquid predecessor—described as a monomer—can harm people at high concentrations and through chronic exposure if it gets into the air.
As heat builds. the chemical can enter a chain reaction known as “thermal runaway. ” where the temperature increase accelerates further heat release. Freeman said excess heat has already caused the MMA to harden and clog the tank’s valves. making it impossible for crews to drain the dangerous chemical or add stabilizing agents.
Covey said crews are now operating with a threshold in mind. “If the temperature of the tank exceeds a certain threshold, ‘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,’” he said.
He compared the potential danger to catastrophic tank failures. “If you’ve ever seen videos of tank cars on a railroad track blowing up. and that fireball it puts out. and it blows half the tank car a half a mile down the train track. that’s the incident potential we are dealing with if this suffers a catastrophic failure. ” Covey said.
Freeman added that another scenario involves a massive leak that could cause significant environmental damage to waterways and the ocean. He said such a leak would eliminate the possibility of a more dangerous explosion, but it would still demand containment and mitigation.
From there, teams in hazardous materials suits would go in and “neutralize and mitigate the vapors that will be coming off of that,” Covey said.
Despite the magnitude of the risk, officials said they believe the evacuation plan is working as designed. Given the size of the evacuation area, “we’re very confident that our evacuation zones mean that anybody outside of that area does not need any personal protective equipment,” Freeman said.
Continuing to pour a deluge of cool water on the tank is meant to change what happens next. Covey said cooling may allow the chemical to cure more slowly—becoming a solid more gradually—and reduce pressure buildup inside the tank.
“Like an ice cube that freezes from the outside in — this stuff cures, it heats up and cures from the outside in. While it’s doing that process, it’s building that pressure,” Covey said.
The tank itself has some capacity to absorb pressure, he said. “We’re hoping that that space can absorb a slower cure rate and not over-pressure and blow up,” Covey said.
Picazo, the assistant professor of chemistry at USC, agreed that time and conditions matter. “One of the best-case scenarios is to let the [MMA] monomers react. but you do it in a controlled way. ” he said. He described another possibility where slower conditions would allow solid material to form inside the tank. potentially keeping reactive monomers separated. “If they don’t come into contact, therefore they cannot react,” Picazo said. “You need contact for reactivity, and you can’t have contact if you have solid state.”.
Firefighters said they were still trying to avoid the worst-case outcome. “We’re optimistic,” Covey said. “We’re bringing people in from all over the country, talking to people all over the place, trying to come up with additional options.”
He said letting the tank fail uncontrolled would be unacceptable to responders. “Letting this thing just fail and blow up is unacceptable to us,” Covey said.
The crisis has also landed on a company already tied to regulatory trouble. In January 2025. GKN Aerospace settled with the South Coast Air Quality Management District for $909. 935.95 over violations of permit requirements. record-keeping requirements. and nitrogen oxide emissions. according to a report posted on AQMD’s website. Neither GKN nor South Coast AQMD immediately responded to questions about the settlement on Saturday.
The damaged tank’s next move—whether it holds under cooling or tips into thermal runaway—will likely determine what the next hours bring for the tens of thousands who have already been forced out of their homes.
Garden Grove GKN Aerospace methyl methacrylate chemical crisis evacuation Gavin Newsom Orange County Fire Authority thermal runaway