No harmful gases were found in the air within a 20km radius of a factory in Nakhon Pathom that had a chemical leak, the Pollution Control Department (PCD) said on Thursday after it conducted an investigation.
The incident happened early on Thursday at a plant owned by Indorama Ventures Plc (IVL) which produces polyester fibres, yarns and chips with a capacity of 120,00 tonnes per year. No serious injuries were reported.
Two chemicals -- diphenyl oxide and biphenyl -- leaked from a heating system's air cooler at the plant in Nakhon Chaisi district.
The leak of "common heat transfer fluid" was detected at 5.45am and was contained within 10 minutes, the listed company said in a statement to the Stock Exchange of Thailand.
"There was no leakage into public waterways or any injury to employees or to the surrounding community or any damage to equipment," company secretary Souvik Roy Chowdhury said.
Some residents 20 kilometres away in tambon Salaya of Phutthamonthon district, which borders Bangkok, said they smelt foul-smelling gases.
Chanthana Pakthongsuk, director of the Region 5 Environmental and Pollution Control Office, who inspected the area, said the office's investigation team found the air quality after the incident was safe and no odour was detected.
Mr Chanthana said the factory staff took about 10 minutes to turn off the faulty valve and stop the leak.
Several nearby educational institutes in Salaya, including Mahidol Wittayasusorn and Kanjanapisek Witthayalai Nakhon Pathom schools, cancelled classes as a result of the leak.
Earlier in the early morning, PCD warned those living nearby to avoid going outdoors unless absolutely necessary. It urged people to wear masks and immediately contact a doctor if they experience difficulty breathing.
Later, it sent a team to inspect the air quality at six schools including Wat Puranawat in Bangkok's Thawi Watthana district, Bang Khu Wat School in Nonthaburi's Bang Yai district and four other schools in Nakhon Pathom.
Dicha Kongsri, director of Thawi Watthana district office in Bangkok, said two students who suffered red eyes and blocked nasal passages received first aid from their teachers.
Nakhon Pathom governor Surasak Charoensiricho said he ordered the temporary suspension of the factory and the closure of nearby schools as part of inspection protocols. He said the leak might have occurred because of the age of the system's hot oil boiler.