Fire officials spent Saturday in an increasingly dire race against the clock at Garden Grove’s GKN Aerospace, with temperatures in a compromised tank of toxic chemicals creeping perilously upward and evacuated residents increasingly worried for their homes and health.
By Saturday morning, it was clear that conditions had worsened inside the failing tank holding an estimated 7,000 liquid gallons of methyl methacrylate, or MMA, making the possibility of a massive explosion or toxic chemical leak at the aircraft and spacecraft manufacturer significantly more likely.
Temperatures inside the tank reached 90 degrees Celsius by 10 a.m. Saturday, up from 77 degrees a day earlier, Craig Covey, Orange County Fire Authority division chief, said during a morning news conference.
An internal sprinkler system supplemented by unmanned ground sprinklers helped stabilize temperatures around 90 degrees, division chief and hazardous materials program manager Nick Freeman said.
Despite firefighters’ round-the-clock efforts, by Saturday afternoon, Freeman said the two most likely outcomes remained dire ones: a massive explosion of the pressurized tank, or a rupture that releases 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.
MMA’s boiling point is 101 degrees Celsius, and the tank’s gauge only detects temperatures up to 100 degrees. Officials haven’t disclosed what temperature they believe would indicate an imminent explosion.
It’s not necessarily the case that the tank would explode at 101 degrees, said Elias Picazo, assistant professor of chemistry at USC.
“It depends on the integrity of the tank, and the composition of the tank, and the pressure capacity of the tank,” Picazo said. “But, yes, above 100, the pressure starts to increase dramatically, because the liquid phase becomes gas phase, and gas takes up any space available. It’ll take up more volume and become highly pressurized.”
By Saturday afternoon, Gov. Gavin Newsom declared a state of emergency over the industrial accident, which has displaced 40,000 people from an evacuation zone that extends roughly a mile in all directions from the aerospace facility and includes parts of Garden Grove, Cypress, Stanton, Anaheim, Buena Park and Westminster.
The California Governor’s Office of Emergency Services has been mobilized since Friday, Newsom wrote on social media, and state agencies are supporting impacted communities to “protect public safety, and assist local officials as response efforts continue.”
“Please continue to follow guidance from emergency officials,” he wrote.
Evacuees gathered at four shelters in Fountain Valley, La Palma, Huntington Beach and Anaheim anxiously awaited updates.
“We left our homes, our memories, everything,” said Nathalie, 45, an Anaheim resident who had 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?”
Based in the United Kingdom, GKN Aerospace manufactures landing gears, jet engines and other materials for commercial and military aircraft.
In January 2025, the company 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.
Firefighters have determined that the emergency was triggered by a failure of the tank’s internal cooling system on Thursday. Late Friday, firefighters had been relying on drone-based thermometers to estimate the temperature inside the failing tank, which gave a reading of 61 degrees, with 50 degrees being the goal.
But by Saturday, Covey said it became clear that the drone could only measure the temperature on the outside of the tank, not the inside. They made that discovery after a crew was sent in overnight and manually read the temperature gauge showing the failing tank’s interior temperature.
“We made a call last night to go back on the offensive,” Covey said. “We did put people in harm’s way last night.”
Inside the tank is an estimated 7,000 gallons of methyl methacrylate, a durable, lightweight and transparent polymer that can be used in household goods or as a glass substitute.
The polymer itself isn’t toxic, but its liquid predecessor — a monomer, essentially a bunch of single molecules — is. If it gets into the air, it can harm people at high concentrations and through chronic exposure.
As the temperature rises, the tank is at risk of falling into a chain reaction known as “thermal runaway,” in which the increase in temperature accelerates further heat release.
Already, the excess heat in the tank has caused the MMA to harden and clog the failing tank’s valves, rendering it impossible for crews to drain the dangerous chemical or add stabilizing agents, Freeman said.
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,” Covey said.
“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,” he said.
Another scenario that could result in significant environmental damage to waterways and the ocean is a massive leak, although such a leak would eliminate the possibility of a more dangerous explosion.
From there, teams in hazardous material suits can go in and “neutralize and mitigate the vapors that will be coming off of that,” Covey said.
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 could allow the liquid chemical inside to cure at a slower rate — become a solid at a slower speed — and reducing the buildup of pressure inside the tank, Covey said.
“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 has some capacity to contain pressure.
“We’re hoping that that space can absorb a slower cure rate and not over-pressure and blow up,” Covey said.
In other words, continuing to cool the tank could slow the chemical reaction in a way that avoids an explosion.
Picazo agreed.
“One of the best-case scenarios is to let the [MMA] monomers react, but you do it in a controlled way,” Picazo said.
“Maybe if it’s slow enough, you can form solid within the tank and cause the monomers, the reactive monomers, to stay apart from one another.”
“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’re hopeful they can still avoid an explosion.
“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.
“Letting this thing just fail and blow up is unacceptable to us,” Covey said.
Times staff writers Andrew Turner, Suhauna Hussain, Hailey Branson Potts, Salvador Hernandez and correspondent Eric Licas contributed to this report.
