SINGAPORE - Eleven workers were taken to hospital after being exposed to a chemical leak at a wafer fabrication plant in Kallang Way on Tuesday (July 18).

The Straits Times understands that the leaked gas was nitrogen trifluoride – a colourless, odourless and non-flammable gas used in the plasma etching of silicon wafers.

The affected workers, who were taken to Tan Tock Seng Hospital, suffered from minor skin irritation, said labour MP Melvin Yong in a Facebook post on Tuesday night. In the post, he expressed relief that all the workers have been "given the green light to be discharged".

All the affected workers were from RF360 Singapore – a joint venture between American telecommunications equipment company Qualcomm and electronics company TDK, which is based in Japan.

Mr Yong, who is tripartism director at the National Trades Union Congress (NTUC), said that RF360 is a unionised company under @UWEEI Singapore.

"The union is in touch with the company to provide the necessary assistance to the affected workers," said Mr Yong, adding that the union will also "follow up closely" with the firm to investigate the incident and ensure workers' safety was not compromised.

The production floor where the leak occurred has been blocked off for investigations, but staff were allowed to go back to work in other parts of the company around 7pm, ST understands.

A staff member, who declined to be identified, said he and other colleagues evacuated the building after hearing an announcement around 12.30pm that there was a gas leak. Workers said they did not smell anything unusual.

The leak was shut off by an in-built safety system before officers from the Singapore Civil Defence Force (SCDF), which was alerted at around 1.40pm, arrived.

SCDF, which sent Hazardous Materials (HazMat) officers to the site, declared around 3pm that the incident was “contained within a sealed production room on the premises”.

At about 3.50pm, the SCDF said its HazMat detectors showed no reading of the chemical vapour in the production room. “The surrounding environment is also safe, with no traces of the chemical in the air,” it added.

When ST was at the scene around 3.30pm, a young woman was seen being escorted to an ambulance. While she looked shaken, she was able to make her own way to it.

A 38-year-old engineer, who declined to be identified, said that the gas alarm had been triggered owing to a leak on the third floor of the building. “I work on the second floor, and it happened in the clean room of a production area,” he said.

He said he was unsure of the headcount during the incident, as it was lunch break at that time.

SCDF officers were seen removing boxes from the premises

In an announcement when the alarm sounded, workers were told to be on “standby” until investigations were completed, he said. He said the company had conducted evacuation drills before for such emergencies.

After the environment was declared safe, workers were told to stay within company premises.

While they were not allowed to re-enter their workplace , they remained in the canteen to wait for further instructions, he added.

During this time, they were asked from time to time if they felt “dizzy or nausea”, said the engineer.

ST has reached out to RF360 Singapore for more information.

In September last year, seven people were sent to hospital after a chlorine gas leak traced to an indoor storage facility at 3, Jalan Samulun.