Construction dust might have set off an old, but popular, fire-extinguishing system at Siam Commercial Bank’s headquarters, killing eight people who didn’t heed a fire alarm.
Bundit Pradabsook, vice president at the Association of Siamese Architects, said on Monday that dust created during an upgrade to the bank's Pyrogen aerosol fire system may actually have triggered it, filling a document vault with chemicals and suffocating seven workers and a security guard. Seven others were hurt, four of them critically.
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"If maintenance is being done in a room where a Pyrogen system is in place, technically the system should be deactivated because its weak point is that it is sensitive to dust," said Mr Bundit.
Pyrogen is a chemical fire retardant normally intended to deprive fire of oxygen and is typically used in places where extinguishing a fire with water would damage documents or equipment.
Pyrogen's website says that its aerosol does not deplete oxygen and is "most effective in unoccupied areas such as data rooms, machinery and engine spaces" and other storage areas. It says people should avoid exposure to Pyrogen and any "accidental exposure to the aerosol should be limited to five minutes."
"The problem with this system in Thailand is that our country is full of dust. Considerable dust can immediately activates a system that is sensitive to particulates of a similar size as in smoke," Mr Bundit added.
He assumed that drilling on a concrete wall in the basement storage room created dust that set off smoke detectors.
Suchatvee Suwansawat, president of the Engineering Institute of Thailand, said a smoke detector sent a signal and then an alarm would ring for five minutes before the Pyrogen canisters were aerosolised.
He added that Pyrogen-based systems were popular in Thailand.
Siriwat Chaichana, secretary-general of the institute, said people who were exposed to the aerosol mist within a range of 10-20 metres would pass out within 15 seconds and die.
Pol Lt Gen Sanit Mahathavorn, acting Bangkok police chief, said after inspecting the SCB headquarters that he had drawn some conclusions about what happened, but would not reveal them right away.
"It's too early to say who is to blame. We need time for experts to investigate the details," The Associated Press reported Lt Gen Sanit telling reporters.
The big question investigators are trying to answer was why those inside the vault did not leave when hearing the fire alarm.
Pol Maj Gen Thawatchai Mekprasertsuk, commander of the Central Police Forensic Science Division, said no workers left the area despite the alarm.
SCB president Yol Phokasub said the bank was replacing its Pyrogen system with a nitrogen-based one. He expressed regret over the accident and said the bank would pay compensation to those injured and the families of the deceased.
