According to China’s Maritime Safety Administration (CMSA), the shipping container explosion aboard the box ship YM Mobility at Ningbo in 2024 was caused by thermal runaway in a cargo of organic peroxides.
The container in question was a refrigerated shipping container filled with tert-butyl perbenzoate (TBPB), a common activator for making plastics like polyethylene and polyester. It becomes unstable at high temperatures, and its safety-critical temperature is 140°F, at which it begins its runaway reaction. This particular shipment was headed to a terminal that requires refrigerated storage for TBPB. Hence, the manufacturer packed it in a refrigerated box so that it could be plugged in on arrival.
YM Mobility’s operator did not require the box to be plugged in while underway. When the container was loaded aboard YM Mobility in Shanghai on August 6, it was stowed as deck cargo on the starboard bow, packed in a refrigerated container, but unplugged and unrefrigerated. Ambient summertime temperatures were about 95°F.
YM Mobility left the Shanghai port on August 7 and sailed to Ningbo. On August 9, a crewmember on duty smelled an “irritating odor” while up on the bow. At about 13:31, he inspected the container involved and noticed a hissing noise, white smoke, and a yellow liquid dripping from the door – characteristic of TPBP decomposition. Over the next six minutes, the smoke increased. The crewmembers on the bow realized the danger and evacuated the area, and the captain sounded the fire alarm to muster the crew.
By 13:38, white smoke obscured most of the starboard bow, and within minutes, it was billowing all over the foredeck. At 13:46:30, the refrigerated container exploded violently, blowing six (6) other containers over the side and disintegrating three (3) more. No injuries were reported, and all crewmembers safely evacuated onto the dock a few minutes later.