Firefighters may have inadvertently caused the massive explosions that devastated Tianjin on Wednesday night, according to chemical experts quoted by Reuters.
The firefighters had been dispatched to put out a container fire at the Ruihai International Logistics warehouse, which police said mainly stored ammonium nitrate, potassium nitrate and calcium carbide.
The firefighters’ use of water to contain the blaze may have contributed to the explosions as water reacts with calcium carbide to create acetylene, a highly explosive gas. Acetylene could have detonated ammonium nitrate, which is also believed to have been present in the warehouse.
Two powerful explosions – the second equivalent to detonating 21 tons of TNT – occurred at around 11:30pm Wednesday night, about 40 minutes after 12 fire crews had been dispatched to the warehouse.
David Leggett, a chemical safety expert based in California, told Reuters the acetylene explosion could have detonated the ammonium nitrate.
"In my mind, the presence of ammonium nitrate makes it easier to explain the level of devastation," he said.
An official from China’s fire department confirmed that the firefighters had used water even though they knew calcium carbide was in the warehouse. A chemical powder is needed to extinguish calcium carbide.
"We knew there was calcium carbide inside but we didn't know whether it had already exploded," said Lei Jinde, the deputy propaganda department head of China’s fire department.
"At that point no one knew, it wasn't that the fire fighters were stupid," Lei said, adding that it was a large warehouse and they didn't know the exact location of the calcium carbide.
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