Photo/IllutrationA Tokyo Fire Department experiment shows the inside of an aluminum can that had melted after being left for six hours with an alkaline cleanser inside it. (Provided by the Tokyo Fire Department)

  • Photo/Illustraion

An accident in which two women were burned when a passenger’s drink bottle burst at Tokyo’s Shinjuku Station this summer was caused by cleaning fluid being wrongly decanted into the aluminum container, according to police.

The finding prompted a warning from an expert that detergents on the market could be turned into lethal weapons by unwitting users who do not know how to store them correctly.

The Tokyo Metropolitan Police Department on Oct. 9 filed criminal papers with prosecutors against a man in his 30s on suspicion of causing bodily injury through negligence. He is suspected of injuring the two women, including a 29-year-old, who suffered minor burns to their faces and legs on a platform at the East Japan Railway Co. station on the early morning of Aug. 26 when the aluminum can burst open after an alkaline detergent caused a build-up of hydrogen gas inside it.

The man allegedly took the industrial-use cleaning fluid from a container at the restaurant where he worked and poured it into a bottle-shaped coffee can with the intention of cleaning his bicycle chain with it. Transferring the detergent into another container is prohibited under the restaurant’s regulations, investigative sources said.

Surveillance camera footage helped identify the man. He was quoted by police as saying, “I didn’t know (the detergent) could have exploded because of a chemical reaction, although I did worry that it could have spilled.”

A similar incident occurred in a train that had stopped at Hongo-sanchome Station on Tokyo Metro Co.’s Marunouchi Line in the capital’s Bunkyo Ward in October 2012.

An aluminum can containing a strong industrial cleaning fluid carried by a passenger exploded in the train, leaving eight passengers with burns on their faces and hands after the liquid burst from the can.

The passenger had been on his way home from work with the container.

Police filed criminal papers with prosecutors against the man in August 2014 accusing him of causing bodily injury through negligence.

According to Katsuhiro Saito, a professor emeritus of organic physics at the Nagoya Institute of Technology, alkaline solutions such as dishwashing detergents cause a chemical reaction when coming into contact with aluminum.

When a can is hermetically sealed with such a fluid inside it, it will become filled with hydrogen gas, building up pressure inside the can and potentially leading to an explosion. The reaction can also result in the alkaline solution bursting out from the can along with the hydrogen gas, the expert said.

Saito also warned that people can suffer burns from being splashed with alkaline solutions, and said that as hydrogen gas is extremely inflammable it can lead to explosions.

“Even acidic cleansers for toilets and other things could also lead to the same type of chemical reaction,” said Saito, stressing the hazardous consequences of transferring such solutions from one container to another.

(This article was written by Shoko Rikimaru and Yosuke Takashima.)