The maintenance of air-conditioning mechanical ventilation (ACMV) ducts within buildings is not subject to regulatory requirements, said the Building and Construction Authority (BCA) in a statement yesterday.
A BCA spokesman told The Straits Times that "building owners are responsible for the maintenance of their buildings, by ensuring that all parts of their buildings are maintained in a state of good and serviceable condition".
This includes the "maintenance of interior fittings such as ACMV ducts", following an incident on Sunday at Nex shopping mall, where a ventilation duct fell in the Shaw Theatres cinema and injured two patrons.
BCA has since instructed the cinema to close for a thorough check, and investigations by an appointed professional engineer are ongoing.
A spokesman from Nex said that "all maintenance of various mechanical and engineering systems for the common areas in the building are carried out according to a planned schedule by appointed specialist contractors".
"In addition, when the maintenance team onsite observes any abnormalities in the course of their work of these systems in the common areas, they will conduct further inspections or checks to determine the cause and take appropriate actions," he said.
The shopping mall is co-owned by Mercatus and Gold Ridge, and managed by the latter.
Associate Professor Daniel Wong from the department of building at the National University of Singapore's School of Design and Environment said the maintenance of duct systems in buildings tends to be very ad hoc and infrequent, owing to the high costs involved and the disruption it causes.
"The suspended ceiling has to be cut open for inspection and cleaning of the duct systems, which are conducted separately - and this is usually very disruptive, hence it is done infrequently," said Prof Wong. Ideally, the inspection of duct systems should be periodically scheduled, but some companies avoid doing maintenance work for as long as five to 10 years, and usually focus on essential or heavy-use areas, he said.