SINGAPORE - One worker has died after inhaling a poisonous gas while carrying out routine tank cleaning at the PUB Choa Chu Kang Waterworks on May 23.

The worker was one of three who had collapsed and were found unconscious. Two of the workers are in the intensive care unit at Ng Teng Fong General Hospital.

PUB in a statement said early investigations suggest that the workers had inhaled hydrogen sulphide, a gas produced from sludge which is a by-product of the water treatment process. 

“As a precaution, PUB has called a safety timeout for similar operations in confined spaces and is reviewing the associated safety measures.”

The Straits Times has contacted PUB for more information.