https://www.straitstimes.com/singapore/worker-dies-2-in-icu-after-inhaling-poisonous-fumes-at-pub-choa-chu-kang-worksite

Early investigations suggest that the workers had inhaled hydrogen sulphide during routine tank cleaning at the Choa Chu Kang Waterworks.

SINGAPORE - A 40-year-old worker has died after inhaling a poisonous gas while carrying out routine tank cleaning at national water agency PUB’s Choa Chu Kang Waterworks on May 23.

The worker – an Indian national – was one of three men aged between 24 and 40 who had collapsed and were found unconscious at the plant at about 11.15am.

All three were taken to hospital unconscious, where the worker died. The two surviving workers are in the intensive care unit at Ng Teng Fong General Hospital, said PUB in a statement.

The two men are Malaysians who are aged 24 and 39, and employed as general workers, said the Ministry of Manpower (MOM) in a statement.

MOM added that the man who died was a cleaning operations manager and, along with the older Malaysian, was employed by Supersonic Maintenance Services. The younger Malaysian works for Stargroup Est.

The ministry said it is investigating and has instructed PUB to stop all tank cleaning work.

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.

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Cleaning works are carried out at the plant routinely once every three months.

In response to queries, the Singapore Civil Defence Force (SCDF) said it was alerted to a hazardous material (hazmat) incident at 51 Nanyang Drive at about 11.25am.

Firefighters and hazmat specialists in personal protective equipment used two water jets to disperse the poisonous gas.

After about an hour of “vapour dispersion”, there was no more hydrogen sulphide detected in the plant, said SCDF.

It added that cardiopulmonary resuscitation, or CPR, was performed on one of the workers on the way to hospital.