Workers who died after inhaling toxic gas did not wear respirators or follow safety protocol, inspector testifies

Mr Srinivasan Sivaraman and Mr Izzat Naqiuddin Dowod died in May 2024 after inhaling hydrogen sulphide, a by-product of the water treatment process.

An aerial shot of Choa Chu Kang Waterworks. (Photo: PUB website)

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SINGAPORE: Two workers who died after inhaling toxic gas entered an enclosed passage at PUB’s Choa Chu Kang Waterworks without respirators and without following safety protocol, the coroner’s court heard on Friday (Oct 2).

Mr Srinivasan Sivaraman and Mr Izzat Naqiuddin Dowod died in May 2024 after inhaling hydrogen sulphide, a by-product of the water treatment process. A third worker survived the incident. Hydrogen sulphide is a colourless, toxic gas that can be fatal at high concentrations.

Mr Muhd Hafidz, an inspector with the Ministry of Manpower’s (MOM) occupational safety and health division, testified in court on Friday that the workers did not ensure that at least one person remained outside the enclosed passage.

Unlike other workers who had entered the passage the day before to drain the tank, the three men did not wear respirators, which are designed to filter out toxic gases. His investigations also found that while there was a ventilator in the passage, it was not in operation at the time, he told the court.

According to the inspector, an external ventilator should have been set up to purge the air as part of safety protocol. The passage was not ventilated before the workers entered.

Mr Sivaraman, a 40-year-old Indian national, was a cleaning operations manager at Supersonic Maintenance Services. Mr Izzat, a 24-year-old Malaysian, worked for Stargroup. Stargroup had been engaged by PUB for "routine" tank cleaning operations at the plant, with Supersonic Maintenance Services as its subcontractor.

Stargroup was charged in July over alleged workplace safety lapses related to the incident – for failing to implement reasonably practicable measures to minimise the risk to any person who may be affected by its undertaking at the workplace.

Stargroup’s authorised manager for confined space entry permits, Lim Beng Hock, was also charged with failing to exercise all due diligence in relation to the issuance of the permits.

Mr Sivaraman and Mr Izzat were part of a team scheduled to clean a tank at PUB's treatment plant.

They had to enter the enclosed passage beneath the tank to drain the water in it before they could clean it, said Mr Hafidz.

Mr Izzat and another worker went through the gate to open all three hand valves while Mr Sivaraman stood outside nearby, in line with the buddy system required by safety protocol. None of them were wearing respirators and the valves were opened within five minutes without incident, the inspector said.

Mr Sivaraman conducted a gas check before the two workers entered the passage, using a personal gas detector that did not sound an alarm, the inspector said.

Mr Hafidz testified that with all three valves open, the wastewater was likely to have been flowing out "quite rapidly", which could have accelerated the release of hydrogen sulphide.

After opening the valves, the workers returned to cleaning the tank above the passage. At about 10am, a worker from another PUB contractor told Mr Sivaraman that the wastewater was flowing rapidly into the next tank and that he had detected a strong rotten smell, the court heard.

Mr Sivaraman instructed an employee to bring someone, go back to the passage and close the valves, the inspector testified.

He also confirmed that nothing had been established about any instructions given by Mr Sivaraman about equipment.

The third worker and Mr Izzat both entered the enclosed passage without respirators. Mr Izzat was wearing a personal gas detector, the inspector said.

The alarm on his personal gas detector, as well as the ones mounted around the passage, were sounding, he added.

This indicated a hazardous environment, but they went into the passage nonetheless, Mr Hafidz said.

When questioned by State Coroner Adam Nakhoda, the inspector confirmed that the workers should not have both entered the passage – one of them should have remained outside.

Citing the third worker’s account of the incident, Mr Hafidz said the worker and Mr Izzat entered the passage and collapsed.

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

He testified that Mr Sivaraman likely entered the passage later to check on the workers or attempt a rescue, before being overcome by the gas.

The three men were found unconscious in the passage. After they were rescued, they were taken to hospital, where Mr Sivaraman and Mr Izzat died.

After the incident, PUB blacklisted Stargroup, barring it from tendering for any of its projects for 18 months from August 2024.

MOM also issued PUB a stop-work order covering cleaning work on pre-treatment water tanks and entry into confined spaces adjacent to the tanks. The order was lifted on Aug 6, 2024, after PUB satisfied the stipulated conditions.

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Srinivasan Sivaraman 先生和 Izzat Naqiuddin Dowod 先生于 2024 年 5 月因吸入硫化氢（水处理过程的副产品）而死亡。

蔡厝港自来水厂的航拍照片。（图片来源：公用事业局网站）

这段音频由人工智能工具生成。

新加坡：验尸法庭周五（10月2日）获悉，两名工人在吸入有毒气体后死亡，他们进入公用事业局蔡厝港水厂的封闭通道时没有佩戴呼吸器，也没有遵守安全规程。

2024年5月，斯里尼瓦桑·西瓦拉曼先生和伊扎特·纳基丁·多沃德先生因吸入硫化氢（水处理过程中的副产品）而死亡。第三名工人幸存。硫化氢是一种无色有毒气体，高浓度时可致命。

人力部职业安全与健康部门的督察员穆罕默德·哈菲兹先生周五在法庭上作证说，工人们没有确保至少有一人留在封闭通道外。

与前一天进入通道排空储罐的其他工人不同，这三名男子没有佩戴呼吸器，而呼吸器是用来过滤有毒气体的。他告诉法庭，他的调查还发现，虽然通道里有一台通风机，但事发时并未运行。

检查员指出，按照安全规程，应该设置外部通风设备进行空气净化。但工人在进入通道前并未进行通风。

40岁的印度籍男子西瓦拉曼先生是超音速维护服务公司的清洁运营经理。24岁的马来西亚籍男子伊扎特先生就职于星集团。星集团受公用事业局委托，负责该工厂的“例行”储罐清洗工作，超音速维护服务公司是其分包商。

Stargroup 于 7 月被指控与该事件相关的工作场所安全疏忽——未能实施合理可行的措施来最大限度地降低其在工作场所开展的活动可能对任何人造成的风险。

Stargroup 的密闭空间进入许可证授权经理林明福也被指控在发放许可证时未能尽到所有应尽的尽职调查义务。

Sivaraman 先生和 Izzat 先生是负责清理 PUB 污水处理厂水箱的团队成员之一。

哈菲兹先生说，他们必须进入水箱下方的封闭通道，将水箱里的水排干，然后才能进行清洗。

伊扎特先生和另一名工人穿过大门打开了全部三个手动阀门，而西瓦拉曼先生则站在附近的外面，这符合安全规程规定的结伴工作制度。检查员说，他们都没有佩戴呼吸器，阀门在五分钟内顺利打开，没有发生任何意外。

检查员称，西瓦拉曼先生在两名工人进入通道前进行了气体检测，他使用的个人气体探测器没有发出警报。

哈菲兹先生作证说，三个阀门全部打开后，废水很可能“很快”流出，这可能会加速硫化氢的释放。

打开阀门后，工人们返回通道上方的水箱继续清理。法庭获悉，大约上午10点，另一家公用事业局承包商的一名工人告诉西瓦拉曼先生，废水正快速流入下一个水箱，而且他闻到了一股强烈的腐臭味。

检查员作证说，西瓦拉曼先生指示一名员工带一个人回到通道，关闭阀门。

他还证实，尚未查明西瓦拉曼先生是否曾就设备发出过任何指示。

第三名工人和伊扎特先生进入封闭通道时都没有佩戴呼吸器。检查员说，伊扎特先生当时佩戴了个人气体检测仪。

他还补充说，他个人的气体探测器以及走廊周围安装的气体探测器都发出了警报。

哈菲兹先生说，这表明环境危险，但他们还是进入了通道。

当州验尸官亚当·纳霍达询问时，该检查员确认，两名工人不应该同时进入通道——其中一人应该留在外面。

哈菲兹先生援引第三名工人的描述称，这名工人和伊扎特先生进入通道后倒下了。

哈菲兹先生表示，调查人员无法确定上午 10 点 30 分到 11 点左右（即发现这三名男子的时间段）之间发生了什么。

他作证说，西瓦拉曼先生很可能是后来进入通道查看工人的情况或试图进行救援，之后才被毒气熏倒。

三名男子被发现昏迷在通道内。获救后，他们被送往医院，其中西瓦拉曼先生和伊扎特先生不幸去世。

事件发生后，公用事业局将星光集团列入黑名单，禁止其从 2024 年 8 月起 18 个月内参与其任何项目的投标。

人力部还向公用事业局发出停工令，禁止其进行预处理水箱的清洁工作以及进入水箱附近密闭空间。在公用事业局满足规定的条件后，该停工令于2024年8月6日解除。

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