Extreme heat shatters records — and windows

The recent heat wave is shattering records — and windows.

The phenomenon, known as thermal stress breakage, occurs when a large temperature difference develops between the center and the edges of a pane of glass. It is especially likely when strong direct sunlight rapidly raises the temperature of the glass.

The breaking itself is a problem enough, but the dangers worsen when the window breaks on a high-rise building, which could potentially cause accidents and injure pedestrians as shards fall.

“Normally, we receive about five or six requests a month to replace broken glass. Last month alone, however, we received more than 15 inquiries involving glass damaged by thermal stress,” said Yoon Ji-young, who runs a glass installation company in Haeundae District, Busan.

“We replaced a cracked window in a high-rise building last Friday. As the extreme heat continues, we’ve also seen several cases where tempered glass on low-rise buildings shattered and fell onto sidewalks.”

On Sunday, a tempered-glass railing on the 15th floor of a high-rise in Jung District, central Seoul, shattered on its own, sending fragments onto a pedestrian walkway below.

Car windows are also vulnerable to heat, especially if they're parked outdoors.

“Most vehicles for sale are parked outdoors, and when daytime temperatures rise to 38 to 39 degrees Celsius (100.4 to 102.2 degrees Fahrenheit), temperatures inside the cars can exceed 70 degrees Celsius,” said an operator of an outdoor used-car dealership in the greater Seoul area. “I worry not just about fires, but about the rear windows cracking on their own.”

Experts said the risk of thermal stress breakage rises as the gap between indoor and outdoor temperatures widens.

“This summer’s heat could be considered an emerging disaster. As heat waves continue, people run their air conditioning harder. When the gap between indoor and outdoor temperatures grows, the temperature across the surface and interior of the glass becomes uneven, increasing the risk of breakage,” said Chae Jin, a professor of fire safety at Mokwon University.

“Aluminum frames absorb large amounts of heat and expand under prolonged exposure, putting extra pressure on the edges of the glass and making thermal stress breakage more likely.”

Experts advised against leaving buildings and vehicles with tempered-glass windows sealed and unattended for extended periods during heat waves.

“Opening a window slightly lets air circulate between the inside and outside of an enclosed space. The resulting convection reduces the temperature difference and helps prevent the glass from breaking,” said Ryu Sang-il, a professor of fire and disaster management administration at Dong-Eui University. “Prolonged heat can also damage the silicone that secures window panes, so it should be checked regularly.”

Meanwhile, a heat wave emergency warning issued for the first time for Seoul and the surrounding metropolitan area on Tuesday remained in effect for a third straight day as of Thursday.

The number of heat-related illnesses and deaths has continued to rise this month. Korea recorded 2,441 heat-related patients and 21 suspected heat-related deaths between May 15 and Tuesday, the Korea Disease Control and Prevention Agency said Thursday.

On Tuesday, 25 spectators were treated for suspected heat-related symptoms during a baseball game between the SSG Landers and LG Twins at Incheon Munhak Stadium.

BY NOH YU-RIM [kim.hayoon1@joongang.co.kr]