Thousands of California residents still can’t go home despite chemical explosion threat over

Thousands of Southern California residents remain displaced from their homes as emergency crews continue efforts to cool a damaged chemical tank at an aerospace plant, despite officials indicating that the immediate risk of a catastrophic explosion has largely subsided.

"It’s not over yet," stated TJ McGovern, interim fire chief of the Orange County Fire Authority, on Monday. "We still have to mitigate a fire and very small explosion concern, and also a spill potential."

Evacuation orders were first issued last Thursday for residents in Garden Grove, near Los Angeles, after the tank began to overheat. Approximately 16,000 individuals out of an initial 50,000 evacuees are still awaiting clearance to return home.

The tank, located at the GKN Aerospace Transparency Systems plant, contains between 6,000 and 7,000 gallons of methyl methacrylate, a highly flammable chemical used in plastics manufacturing.

Exposure to this substance can lead to severe respiratory and neurological problems, as well as irritation of the skin, eyes, and throat, according to the federal Environmental Protection Agency.

An evaluation of the tank revealed a reduction in internal pressure, attributed to a crack discovered on Sunday.

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The interior temperature had cooled to 93 degrees F (33.9 degrees C) by Monday, down from 100 degrees (37.7 degrees C) the previous day, according to county fire division chief Craig Covey.

The company reported that its technical specialists, alongside the county fire authority, have removed insulation from the tank to aid in the cooling process.

Health officials have sought to reassure residents returning to areas near the plant. "There was no contamination. There were no fumes. There were not vapors that came from this incident," Orange County Health Director Regina Chinsio-Kwong said at Monday's news conference.

"There was not a leak. So it should be, you should feel comfortable going home even if you’re across the street from that new zone line." The South Coast Air Quality Management District will monitor air quality for several months, while the EPA will inspect sewer and storm drains for any spills, Orange County Supervisor Janet Nguyen confirmed.

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Residents expressed a mix of relief and caution. Kim Yen, a retiree whose home is two blocks from the plant, is eager to return but prioritizes safety.

"I am happy and many of us are happy but, still, we are still on our evacuation," she said Monday, also praising the emergency crews as "our heroes." A large park in Fountain Valley served as an ad hoc shelter, with its parking lot full of evacuees and tents pitched outside.

Despite the progress, environmental risks persist. Andrew Whelton, a Purdue University engineering professor specializing in environmental contamination, explained that as the tank heated, the chemical converted from liquid to gas, increasing pressure and explosion risk.

He noted that some methyl methacrylate might have solidified into a stable plastic, similar to plexiglass, which would reduce the danger.

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However, Whelton cautioned that an explosion risk remains while the chemical is hot and reactive, stating that temperatures need to drop closer to 60 to 70 degrees Fahrenheit (15.6 to 21.1 degrees C) for conditions to be considered significantly safer.

GKN Aerospace Transparency Systems, a British company, manufactures cockpit windows, canopies, and windshields for military and commercial aircraft, employing approximately 16,000 people across 32 sites in 12 countries. The company issued an apology, stating, "We apologize for the ongoing disruption this incident is causing and our priority remains its safe resolution, so that residents can return to their homes as quickly as possible." GKN Aerospace previously agreed in 2025 to pay state regulators over \$900,000 to settle violations related to recordkeeping, permitting issues, and nitrogen oxide emissions, according to a report on the South Coast Air Quality Management District website.

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