Coupang warehouse burned for 109 hours, but fire stayed contained — noncombustible panels get a second look

As large-scale fires at major distribution centers — including the Coupang Inc warehouse in Incheon — continue to break out, the fire safety of building materials is drawing attention as a key factor in determining the scale of damage. Large logistics facilities carry a high "fire load," meaning they contain large quantities of combustible materials. How effectively the spread of flames can be suppressed may ultimately be the deciding variable in how much damage a fire causes.

According to industry sources Thursday, Coupang Inc's No. 32 distribution center in Seoknam-dong, Seo-hae District, Incheon, used composite panels — commonly known as sandwich panels — with glass wool cores that meet noncombustible performance standards. While the fire burned for an extended period due to the large volume of combustible goods stored inside, experts say the rapid vertical spread of flames up the exterior walls was relatively contained.

"The distribution center was designed from the outset with glass wool panels, which offer the highest resistance to combustion," a National Fire Agency official said. "The use of Class 1 noncombustible materials for the exterior cladding helped prevent the fire from spreading along the outer walls in the early stages."

Industry experts agree that when it comes to fire spread, what matters more than whether a sandwich panel was used is what type of insulation is inside it. Sandwich panels consist of insulation material sandwiched between steel sheets and are widely used in factories, distribution centers and warehouses for their ease of installation and strong thermal performance. When a fire breaks out, the type and performance of the core material can significantly affect how quickly flames spread and how extensive the damage becomes.

In the past, sandwich panels often used combustible core materials. When organic insulation such as polyurethane (PUR), polyisocyanurate (PIR) or expanded polystyrene (EPS) is used, fire that reaches the panel interior can ignite the insulation itself, accelerating the spread of flames. This has repeatedly led to fires racing up exterior walls and jumping to adjacent floors. The steel outer sheets also block firefighting water from penetrating to the interior, making suppression difficult. The 2020 fire at a Han Express warehouse construction site in Icheon, which killed 38 people, is the most prominent example.

In response to such disasters, the government has steadily tightened standards for building materials. Requirements for quasi-noncombustible or higher performance in composite materials and insulation have already been introduced. On July 23, the National Assembly passed an amendment to the Building Act mandating fully noncombustible materials for interior finishes in underground parking lots.

The Coupang Inc warehouse fire is being assessed as a case that illustrates how fire-resistant building materials can limit the spread of damage in a major blaze. "In past warehouse fires, flames often raced up exterior walls to upper floors, but in this fire, vertical spread through the exterior walls appears to have been substantially controlled despite the prolonged burning," said Lee Young-ju, a professor in the fire and disaster prevention department at Kyungil University. "Rather than simply arguing that inorganic core materials must always be used, it is more reasonable to see this as the result of strengthened quasi-noncombustible performance standards working in tandem with manufacturing and quality-control systems," Lee added.