Explosion threat eased after crack cools leaking chemical tank in Orange County

The risk of a catastrophic blast at a Garden Grove chemical plant was ruled out Monday after a crack in a failing tank relieved pressure, but officials said the danger was not fully gone. A smaller explosion or spill remained possible at the GKN Aerospace Transparency Systems facility at 12122 Western Ave., where a 34,000-gallon storage tank holding about 7,000 gallons of methyl methacrylate overheated and began venting vapors.

Orange County fire crews first confronted the incident Thursday, May 21, 2026, and warned that the tank could rupture or trigger a thermal runaway event. By Monday, interim Orange County Fire Chief TJ McGovern said the threat of a BLEVE, or boiling liquid expanding vapor explosion, was "off the table." Division Chief Craig Covey said the crack discovered Saturday night appeared to lower the pressure inside the tank and bring its internal temperature down from 100 degrees Fahrenheit to 93 degrees.

That shift eased the most severe public safety concern, but it did not undo the wider disruption. Evacuation orders swept through parts of Garden Grove, Anaheim, Buena Park, Cypress, Stanton and Westminster, pushing roughly 40,000 to 50,000 people out of their homes. Some evacuees slept in shelters, while others stayed in cars or with relatives as officials mapped blast zones that could have included severe, moderate and light damage areas, along with flammability and health-risk zones that could shift with the wind.

The human toll was immediate and personal. One evacuee told NBC News she felt "nervous, scared, devastated" and said she had gone without medication and basic needs while sleeping in her car. Orange County health officials warned that methyl methacrylate exposure can irritate the lungs and nasal passages, cause dizziness and nausea, and at high levels lead to severe respiratory distress that may require hospitalization.

The emergency also escalated into a policy test for local and state leaders. Gov. Gavin Newsom declared a state of emergency in Orange County on Saturday, May 23, and his office said California requested a federal emergency declaration from President Donald Trump to bolster response operations. The Orange County District Attorney’s Office opened an anonymous tip hotline and online reporting form, while evacuation centers remained open for displaced residents.

The incident has already moved into court, with a class-action lawsuit filed against GKN Aerospace on behalf of evacuated residents. Officials said they had not found a similar precedent for this kind of hazmat emergency as they continued working with the Environmental Protection Agency and the South Coast Air Quality Management District to monitor the site and the surrounding community.