What happened

While removing a malfunctioning gearbox from a plug valve during maintenance, workers released about 2,000 pounds of pressurised isobutane, forming a vapor cloud that reached a welding operation 70 feet away and ignited. Four workers suffered critical burns and two more had minor injuries. The CSB attributed the release to an outdated, decades-old valve design; OSHA later fined ExxonMobil roughly $165,000 for inadequate training and maintenance. This was an accidental industrial incident, not an attack.

When cited sources give different casualty, damage or spill figures for this event, they’re reported side by side above rather than merged into one number. See how confidence levels work.