A 40-year-old Indian national passed away on Thursday due to inhaling poisonous gas while performing routine tank cleaning at a waterwork site in Singapore. The Indian national, along with two other men aged between 24 and 40, collapsed and were found unconscious at the Choa Chu Kang Waterworks of the waterworks agency around 11:15 am, as reported by The Straits Times. All three individuals were taken to the hospital unconscious, where the worker succumbed to the incident. The two surviving workers, Malaysians aged 24 and 39 employed as general workers, are currently in the intensive care unit at Ng Teng Fong General Hospital, according to a statement from the Public Utilities Board (PUB). The deceased Indian national worked as a cleaning operations manager for Supersonic Maintenance Services, as mentioned in a report by the Channel News Agency, citing a Ministry of Manpower spokesperson. The Ministry of Manpower (MOM) stated that it is investigating the matter and has directed PUB to halt all tank cleaning operations. Initial investigations by PUB suggest that the workers might have inhaled hydrogen sulfide, a gas derived from sludge, a byproduct of the water treatment process. Cleaning activities are typically conducted at the plant every three months. The Singapore Civil Defence Force (SCDF) responded to a hazardous material incident at 51 Nanyang Drive, employing firefighters and hazmat specialists in personal protective gear using water jets to disperse the toxic gas. After approximately an hour of vapor dispersion, SCDF reported no further detection of hydrogen sulfide at the plant and informed that CPR was administered to one of the workers en route to the hospital. The police have confirmed no foul play in the incident. Hydrogen sulfide, a colorless gas with a smell resembling rotten eggs, can cause irritation to the eyes and respiratory system, leading to severe health complications. Workers in wastewater treatment industries are particularly vulnerable to such risks, as stated on the United States National Institute for Occupational Safety and Health (Niosh) website. Choa Chu Kang Waterworks plays a crucial role in Singapore's water security strategy, providing 80 million gallons of safe drinking water to the western part of the island, as outlined in an environmental impact assessment from 2022. Plant upgrades commenced in 2022 and are scheduled for completion by 2026.