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That's the nightmare scenario. Each molecule of heat accelerates the reaction. Each acceleration produces more heat. There is no ceiling. There is no circuit breaker. The process feeds itself until the tank can no longer contain the pressure — at which point, it explodes.

The GKN facility holds a 34,000-gallon storage tank of this material. The industrial tank is estimated to contain 7,000 gallons of methyl methacrylate, described by fire officials as "highly volatile" and "highly flammable." Surrounding it are additional tanks containing fuel and other chemicals — each one a potential secondary explosion if the primary tank ignites.

'Two Options. Neither of Them Good.'

Orange County Fire Authority Division Chief Craig Covey did not mince words at Friday's press conference.

"The tank that is in the biggest crisis is in fact unable to be secured and mitigated. There are literally two options left remaining. One, the tank fails and spills a total of about 6,000 to 7,000 gallons of very bad chemicals into the parking lot in that area, or two, the tank goes into a thermal runaway and blows up, affecting the tanks that are around them that have fuel or the chemicals in them as well."

Covey described the valve as broken and "gummed up," adding: "This thing is going to fail. I don't know when."

Read that again. A Division Chief of one of the most experienced fire agencies in California — a man with hazmat crews, the tank manufacturer's own technical representatives, and specialized response teams at his disposal — looked into the cameras and said: I don't know when.

That's not a routine industrial incident. That's a countdown.

Officials described two remaining outcomes: the tank fails and spills roughly 6,000 to 7,000 gallons of chemical, or it goes into thermal runaway and explodes — with other nearby tanks in the blast radius.

Methyl methacrylate is a monomer kept stable by a small amount of inhibitor that only works while dissolved oxygen is present. Heat consumes both the oxygen and the inhibitor. Once polymerization starts it is exothermic and self-accelerating, so adding more inhibitor cannot reverse it. By the time the reaction is running, there is no chemical fix available.

In plain terms: the moment that reaction begins in earnest, the outcome is no longer in human hands.

What Happens If It Blows?

If the tank enters full thermal runaway and explodes, the consequences extend far beyond the GKN fence line.

An uncontrolled release of thousands of gallons of burning, vaporizing methyl methacrylate — surrounded by additional tanks containing fuel — would send a toxic plume of flammable vapor into a densely populated residential community. Orange County Health Officer Regina Chinsio-Kwong warned that an explosion could cause the chemical to be released as a vapor which, if inhaled, could cause "severe respiratory issues." Other symptoms include a sore throat, runny nose, itchy and burning eyes, and potentially nausea and headache.