Workers who died after inhaling toxic gas at PUB facility did not wear respirator masks: Investigator

Published Oct 02, 2026, 05:29 PM

Updated Oct 02, 2026, 05:29 PM

Two workers died after inhaling toxic hydrogen sulphide gas at PUB’s Choa Chu Kang Waterworks without wearing respirator masks.

Safety measures like ventilation, buddy system were ignored, leading to the fatal incident during sludge tank cleaning, according to an MOM investigation officer.

MOM charged the cleaning company and worksite manager; PUB received a fine.

SINGAPORE – The two workers who died after inhaling toxic gas at PUB’s Choa Chu Kang Waterworks were not wearing respirator masks, said a Ministry of Manpower (MOM) investigating officer on Oct 2.

Several other safety protocols were also not followed, including the requirement to ventilate the area before entry, said Muhd Hafidz, a senior investigating officer with MOM’s occupational safety and health division.

He was testifying on the first day of a coroner’s inquiry into the deaths of the two workers.

Malaysian Izzat Naqiuddin Dowod, 24, and Indian national Srinivasan Sivaraman, 40, collapsed after inhaling hydrogen sulphide, which is produced by sludge, a by-product of the water treatment process.

Hydrogen sulphide is colourless and can be lethal even at low concentrations.

Izzat and a third worker entered the enclosed passageway of the pulsator tank to turn off a valve controlling the drainage of sludge on the morning of May 23, 2024.

Sivaraman likely entered the gallery shortly after to check on them, said the investigator.

He added that both Izzat and Sivaraman were not wearing respirator masks when they were rescued.

Sivaraman succumbed to his injures on the day of the incident , while Izzat died on May 28 .

The third worker survived the incident.

Izzat was employed by Stargroup Est, a cleaning company, while Sivaraman was a cleaning operations manager at Supersonic Maintenance Services.

Hafidz told the court that a cleaning team, including the two deceased, were supposed to carry out cleaning works on the pulsator tanks that day.

Safety protocols required workers entering the gallery of the pulsator tank to have a personal gas detector and a personal torchlight.

They must also have a buddy who was supposed to stand outside the passageway.

Before entering the passageway , external ventilation had to be done to dissipate the toxic gases.

The passageway has three alarms, which will alert workers when the environment is hazardous.

All three alarms were working on the day of the accident, said the investigation officer.

At about 9.30am that day, Izzat and another worker entered the passageway to turn on the valve to drain the sludge.

Sivaraman was standing outside, following the buddy system.

The two workers opened the valve and left without any incident.

Around 10am, a contractor noticed a foul smell coming from the tank, and realised that the sludge was flowing out too rapidly.

The contractor informed Sivaraman, who instructed Izzat and the worker to go back to the passageway to close the valve.

The two men entered the area without respirators, and collapsed after inhaling hydrogen sulphide.

Izzat was wearing a personal gas detector, according to Hafidz.

No ventilation of the area was done prior to their entry, said the investigator, adding that the two men did not have a buddy standing outside the gallery.

The alarms inside the gallery were triggered at the time, he said. However, this was expected due to the release of toxic gases during the cleaning of the tanks.

The alarm on Izzat’s gas detector had also been activated.

Hafidz said investigators could not establish what happened between 10.30am and about 11am, when the three men were found inside the passageway.

The Singapore Civil Defence Force was called to the scene. Firefighters and hazmat specialists in personal protective equipment used two water jets to disperse the poisonous gas .

All three workers were taken to Ng Teng Fong General Hospital.

Stargroup Est was charged in July over allegedly failing to implement “reasonably practicable measures” to minimise the risk to individuals at the workplace on or before May 23, 2024.

Worksite manager Lim Beng Hock was given 12 charges.

The 49-year-old is said to have failed to exercise due diligence in the issuance of confined space entry permits.

After the incident, MOM issued a stop-work order to PUB.

The agency had to cease cleaning work on the water tanks and stop entry into confined spaces adjacent to the tanks.

The stop-work order was lifted on Aug 6, 2024, after PUB met the conditions set by MOM.

PUB said in July that it was issued a composition fine by MOM. One of their staff members was also issued a stern warning.

发布于 2026 年 10 月 2 日 下午 5:29

更新于2026年10月2日下午5:29

两名工人在新加坡公用事业局蔡厝港自来水厂吸入有毒的硫化氢气体后死亡，原因是他们没有佩戴呼吸面罩。

据人力部调查官员称，通风、伙伴制度等安全措施被忽视，导致污泥池清理过程中发生致命事故。

人力部对清洁公司和工地经理提出指控；公用事业局被处以罚款。

新加坡——人力部一名调查官员于10月2日表示，在公用事业局蔡厝港水厂吸入有毒气体后死亡的两名工人当时没有佩戴呼吸面罩。

人力部职业安全与健康部门高级调查员穆罕默德·哈菲兹表示，其他几项安全规程也没有得到遵守，包括进入前必须对该区域进行通风的要求。

在验尸官对两名工人死亡事件展开调查的第一天，他出庭作证。

24 岁的马来西亚人 Izzat Naqiuddin Dowod 和 40 岁的印度公民 Srinivasan Sivaraman 在吸入硫化氢后昏倒，硫化氢是由污泥产生的，污泥是水处理过程的副产品。

硫化氢是无色的，即使浓度很低也能致命。

2024 年 5 月 23 日上午，伊扎特和第三名工人进入脉动池的封闭通道，关闭控制污泥排放的阀门。

调查人员表示，西瓦拉曼很可能随后进入了画廊查看情况。

他还补充说，伊扎特和西瓦拉曼获救时都没有佩戴呼吸器面罩。

西瓦拉曼在事发当天因伤势过重去世，而伊扎特于 5 月 28 日去世。

第三名工人在这起事故中幸存了下来。

Izzat 受雇于 Stargroup Est 清洁公司，而 Sivaraman 是 Supersonic Maintenance Services 的清洁运营经理。

哈菲兹告诉法庭，包括这两名死者在内的一个清洁小组原本应该在当天对脉动罐进行清洁工作。

安全规程要求进入脉冲罐通道的工人必须携带个人气体探测器和个人手电筒。

他们还必须有一个同伴站在通道外面。

进入通道前，必须进行外部通风以驱散有毒气体。

通道内设有三个警报器，当环境危险时会向工人发出警报。

调查人员表示，事故发生当天，三个警报器均处于正常工作状态。

当天上午 9 点 30 分左右，伊扎特和另一名工人进入通道，打开阀门排出污泥。

西瓦拉曼站在外面，遵循结伴而行的原则。

两名工人打开阀门后离开，没有发生任何意外。

上午 10 点左右，一名承包商注意到水箱里散发出难闻的气味，并意识到污泥流出的速度太快了。

承包商通知了西瓦拉曼，西瓦拉曼指示伊扎特和工人回到通道关闭阀门。

两名男子进入该区域时未佩戴呼吸器，吸入硫化氢后倒地。

据哈菲兹称，伊扎特当时佩戴着个人气体探测器。

调查人员表示，两人进入该区域前并未进行通风，并补充说，这两名男子在画廊外也没有同伴。

他说，当时展厅内的警报响了。不过，这是意料之中的，因为在清洗储罐的过程中释放了有毒气体。

伊扎特的燃气探测器警报也响了。

哈菲兹表示，调查人员无法确定上午 10 点 30 分到 11 点左右之间发生了什么，当时这三名男子被发现在通道内。

新加坡民防部队接到报警后赶到现场。消防员和身穿个人防护装备的危险品处理专家使用两支水枪驱散有毒气体。

三名工人全部被送往黄廷方综合医院。

Stargroup Est 于 7 月被指控未能实施“合理可行的措施”来最大限度地降低 2024 年 5 月 23 日或之前工作场所个人面临的风险。

工地经理林明福被控12项罪名。

据称，这位 49 岁的男子在签发密闭空间进入许可证时未能尽到应有的谨慎义务。

事件发生后，人力部向公用事业局发出停工令。

该机构不得不停止对水箱的清理工作，并停止进入水箱附近的密闭空间。

2024 年 8 月 6 日，在公用事业局满足人力部设定的条件后，停工令被解除。

公用事业局（PUB）7月份表示，人力部（MOM）已对其处以罚款。其一名员工也受到了严厉警告。