A fire broke out at SK Hynix’s Cheongju campus on June 1 at approximately 10:32 a.m. local time, triggering the evacuation of around 3,600 workers from the facility. The blaze, which started in a gas room serving the M15 and M15X production lines, was quickly extinguished by automated sprinklers, but not before releasing hydrogen fluoride gas into the area.

Hydrogen fluoride is a highly corrosive compound used extensively in semiconductor manufacturing for etching silicon wafers. The peak concentration reached approximately 5 parts per million, a level that can cause irritation but sits below the threshold for severe health consequences with short-term exposure.

Six to seven workers were treated for eye irritation following the incident. No serious injuries were reported. Air quality tests conducted afterward confirmed the area was safe, and most employees returned to work roughly 90 minutes later.

What happened at the Cheongju facility

The fire originated during routine pipe maintenance, with a minor spark setting off the chain of events. SK Hynix confirmed that semiconductor production continued as usual throughout the incident. Automated safety systems did exactly what they were designed to do, containing the fire before it could spread or cause meaningful damage to equipment.

Hydrogen fluoride exposure at 5 ppm can cause eye and respiratory irritation, which tracks with the symptoms reported by the six to seven employees who received treatment. For context, the US Occupational Safety and Health Administration sets the permissible exposure limit for HF at 3 ppm over an eight-hour workday, meaning the peak reading briefly exceeded that benchmark, though the exposure window was far shorter than eight hours.

SK Hynix’s growing importance in the AI supply chain

SK Hynix has cemented itself as a dominant force in high-bandwidth memory, the specialized chips that power AI accelerators from Nvidia and other companies racing to build out artificial intelligence infrastructure. SK Hynix recently crossed a landmark threshold by joining the $1 trillion market capitalization club. The company sits alongside rivals like Micron in the memory chip space, but it has maintained a notable lead in HBM production specifically.

Any production disruption at a facility like Cheongju would send ripples through an already-strained AI chip supply chain. The fact that this incident caused zero production impact is the most closely watched detail by customers and investors alike.

What this means for investors

Production wasn’t interrupted, no one was seriously hurt, and the company’s safety systems performed as intended. The more significant concern is concentration risk: SK Hynix’s Cheongju campus houses some of the most advanced memory chip production capacity on the planet. A more severe incident could have cascading effects on AI chip availability globally.

The semiconductor industry has learned this lesson repeatedly, from the 2021 Samsung Austin fab shutdown caused by a Texas winter storm to various earthquake-related disruptions at Japanese chip facilities over the years. SK Hynix’s $1 trillion valuation prices in continued dominance in HBM and steady production growth.