Nearly two years after two workers died from toxic gas exposure inside a water treatment tank in Singapore, the contractor responsible and its manager have been formally charged with workplace safety failures. The men, employed by Stargroup, descended into a confined passage at Choa Chu Kang Waterworks on May 23, 2024, where hydrogen sulphide released from settled sludge overcame them — even as sensors detected dangerous levels and alarms sounded. The charges, alongside fines and warnings issued to the national water agency PUB, reflect a broader reckoning with the distance that so often exist
Contractor charged after toxic gas deaths at Singapore water treatment facility
Two workers died from hydrogen sulphide gas exposure; a third was hospitalized but discharged after treatment.
The alarm had sounded. No one had acted on it in time.
Mark
Why did it take nearly two years to charge the contractor after the deaths?
Mimi
The investigation itself takes time—determining what happened, who knew what, what safety measures existed and which ones failed. But the delay also reflects how these cases move through the system. The deaths occurred in May 2024. The charges came in July 2026. That's the pace of workplace safety enforcement.
Mark
The sensors detected the gas and the alarm sounded. So why didn't anyone stop the workers from entering?
Mimi
That's the core failure. The equipment worked. The warning system worked. But there was no one listening, or no one with the authority or training to act on it. That's why the PUB officer received a warning—he didn't cooperate with his employer to ensure compliance that night. The system broke at the human level.
Mark
Hydrogen sulphide is described as lethal even at low concentrations. How much exposure kills?
Mimi
It's insidious precisely because you can't see it or smell it reliably at dangerous levels. The gas itself is colorless. Workers can be overcome without realizing they're in danger. That's why confined space work requires so much preparation—ventilation, testing, protective equipment, a trained person standing by. You're working against an invisible threat.
Mark
What does it mean that PUB had allowed workers to enter confined spaces without adequate ventilation on previous occasions?
Mimi
It suggests this wasn't a one-time oversight. It was a pattern. The company had been cutting corners on safety before the deaths. The fine and the stop-work order were meant to force a change in how PUB operates. Whether they succeeded is another question.
Mark
The third worker survived. What does that tell us?
Mimi
It tells us the exposure wasn't uniform—perhaps he was closer to the entrance, or the gas concentration varied. But it also means two families lost someone while a third person lived with whatever trauma and physical effects came from that day. The survival doesn't erase the loss.
The Pulse
- Sensors detected lethal hydrogen sulphide levels and alarms triggered, yet three workers still entered the confined space without adequate protection — two would not survive.
- The deaths exposed a systemic gap: safety procedures existed in policy but had not been enforced in practice, implicating both the contractor and the national water agency that hired them.
- Nearly two years of investigation culminated in formal charges against Stargroup and its authorized manager, while PUB was fined and one of its officers formally warned for their own failures.
- MOM imposed a stop-work order lasting over two months, halting all confined space operations at pre-treatment water tanks until PUB could demonstrate genuine compliance.
- Authorities have now mandated that confined space work require risk assessments, atmospheric testing, respiratory equipment, and a trained standby person — standards that should have been in place all along.
Nearly two years after two workers died from toxic gas exposure inside a water treatment tank in Singapore, the contractor responsible and its manager have been formally charged with workplace safety failures. The men, employed by Stargroup, descended into a confined passage at Choa Chu Kang Waterworks on May 23, 2024, where hydrogen sulphide released from settled sludge overcame them — even as sensors detected dangerous levels and alarms sounded. The charges, alongside fines and warnings issued to the national water agency PUB, reflect a broader reckoning with the distance that so often exists between safety protocols written on paper and the realities faced by workers in the field.
On May 23, 2024, four workers arrived at Choa Chu Kang Waterworks for what their employer described as routine tank cleaning. Three of them descended into an enclosed passage beneath a drained water treatment tank to close hand valves. What they were not adequately prepared for was the hydrogen sulphide silently accumulating from sludge at the bottom — a colorless, fast-acting gas that kills with little warning. All three collapsed. They were rushed to Ng Teng Fong General Hospital. Two died within days; the third survived.
Investigations by the Ministry of Manpower confirmed that safety sensors had detected dangerous gas levels and alarms had sounded before the workers entered. No one had acted on those warnings in time. The failure was not one of ignorance but of practice — protocols existed, and were ignored.
On July 16, 2026, nearly two years after the deaths, Stargroup was formally charged with failing to implement reasonably practicable safety measures. The company's authorized manager for confined space entry permits, Lim Beng Hock, was also charged for not exercising due diligence when issuing those permits. Accountability reached further still: PUB, the national water agency that had contracted Stargroup, was fined for allowing its own employees to enter confined spaces on prior occasions without adequate ventilation, and a PUB officer was warned for failing to cooperate with workplace safety obligations the night before the incident.
In the aftermath, MOM issued a stop-work order halting all confined space operations near pre-treatment tanks — an order that remained in force for more than two months. Authorities have since made explicit what should always have been standard: risk assessments before entry, atmospheric testing, respiratory protective equipment, and a trained standby person stationed outside at all times. The two deaths forced a hard reckoning with how Singapore's water authority managed one of its most hazardous operations. Whether that reckoning would be enough to prevent the next tragedy remained an open question.
On May 23, 2024, four workers arrived at Choa Chu Kang Waterworks to perform what their employer called routine work—cleaning a water treatment tank. Three of them would not leave the site on their own feet.
The men, employed by Stargroup and a subcontractor, had been tasked with entering an enclosed passage beneath the tank to close hand valves. Water had been drained from the tank earlier that day. What no one adequately prepared them for was what happens when sludge settles at the bottom of such tanks: it releases hydrogen sulphide, a colorless gas that kills quickly and without warning, even in small amounts.
Three workers descended into that passage. Within hours, all three had collapsed. They were rushed to Ng Teng Fong General Hospital. Two died—one on May 24, the other four days later on May 28. The third survived, discharged after medical care. The Ministry of Manpower's investigation later confirmed what the sensors at the site had already detected: hydrogen sulphide levels had exceeded safe thresholds. The alarm had sounded. No one had acted on it in time.
On Thursday, July 16, 2026—nearly two years after the deaths—Stargroup was formally charged with failing to implement reasonably practicable safety measures to protect workers from hazards at the site. Lim Beng Hock, the company's authorized manager for confined space entry permits, was also charged for not exercising due diligence when issuing those permits. The charges represent the legal system's delayed reckoning with what happened in that tank.
But the accountability extended beyond the contractor. The Ministry of Manpower issued a stern warning to a PUB officer for failing to cooperate with his employer in meeting workplace safety obligations on the night before the incident. PUB itself—the national water agency that had hired Stargroup—was fined for allowing its own employees to enter confined spaces on previous occasions without adequate ventilation. The pattern was clear: safety protocols existed on paper but not in practice.
The ministry's statement that followed the charges read like a manual for what should have happened. Employers conducting confined space work must conduct risk assessments before operations begin. They must test the atmosphere inside the space. They must provide workers with appropriate respiratory protective equipment. They must station a trained standby person outside at all times. Workers, in turn, must comply with all safety requirements and follow procedures. None of this was optional or negotiable.
After the incident, MOM issued a stop-work order halting all cleaning operations on pre-treatment water tanks and entry into confined spaces near them. The order remained in place for more than two months until August 6, 2024, when PUB demonstrated it had satisfied the required conditions to resume work. The two deaths had forced a reckoning with how the nation's water authority managed one of its most dangerous operations. Whether that reckoning would prevent the next tragedy remained to be seen.
Notable Quotes
Employers carrying out work in confined spaces are legally required to conduct risk assessments, test the atmosphere, provide respiratory protective equipment, and ensure a trained standby person is stationed outside at all times.— Ministry of Manpower
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