A toxic gas leak that hospitalised workers at Woden Plaza will force urgent checks on the territory's dry cleaners, after early investigations suggested it was caused by inadequate maintenance.
Potentially fatal carbon monoxide is thought to have leaked from a faulty boiler at Bell's Dry Cleaners at Bonner House, adjacent to Woden Plaza, on Sunday.
The gas flowed up through an airconditioning unit, and leaked into a neighbouring alterations shop.
Two alteration workers collapsed, as did a security guard who went to their aid, while a paramedic and a Bell's employee were affected. The alterations workers and Bell's employee were kept overnight in hospital and discharged on Monday.
It is still unclear how long they had been inhaling the carbon monoxide, but they are not understood to have any permanent injury. Investigators from WorkSafe ACT returned to the site on Monday morning.
WorkSafe now believes the leak was caused by ''maintenance shortcomings'' on the boiler, and are now preparing to inspect maintenance records for all similar equipment in use across the ACT.
Work Safety Commissioner Mark McCabe said it was unclear how extensive the maintenance failures were at the Woden shop.
''We're almost certain now that the fault is from a faulty boiler in the dry cleaning company,'' Mr McCabe said. ''We've got a firm belief now that those maintenance issues probably led to the incident.''
But Bell's Dry Cleaners owner Julian Moufarrige said the boiler was only two years old, and was checked annually for faults.
Mr Moufarrige said the business, which has operated from the site for 35 years, would do everything it could to ensure the incident was not repeated.
He said he spoke with the alterations staff on Sunday night, and that they bore no animosity against the dry cleaners.
''I think they're just glad that it wasn't more serious, as we all are,'' Mr Moufarrige said. ''We had no warning obviously, we've got alarms on the boiler … but there was no alarm going off.''
Work safety officers will now begin contacting dry cleaners in the ACT to check maintenance procedures for similar boilers.
They are awaiting a report from an independent expert before starting the process. ''It really is a precaution to make sure a similar issue doesn't arise elsewhere,'' Mr McCabe said.