The NSW government knew two years ago that the Calvary Mater's heating, ventilation and air-conditioning (HVAC) system had to be fixed because it was causing "poor outcomes for hospital staff and patients".
The flawed HVAC has been a key issue at the NSW parliamentary inquiry into the Mater mould and maintenance scandal.
The inquiry's third hearing will be held on Thursday.
Documents tabled with the inquiry have pinpointed the HVAC system, along with faulty building cladding that caused water leaks, as the cause of deadly mould contamination at the hospital.
NSW Health commissioned independent consultant Covaris to do an engineering review for Hunter New England Health (HNEH) in 2023-24 for "maintenance improvement" at the Mater.
The engineering report, dated June 2024, confirmed that the HVAC system had "no dehumidification".
"There is no equipment integrated into the HVAC systems to control the relative humidity across the hospital," the report said.
"The Mater's HVAC system is not up to task as it cannot control relative humidity, and this has led to poor outcomes for hospital staff and patients."
Inquiry chair and Greens MLC Amanda Cohn said the report "should have prompted action two years ago".
"Instead, improvement works didn't start until earlier this year, when the situation had already escalated to the point of wards being closed for patient safety," Dr Cohn said.
"What was the point of commissioning an engineering review if its findings weren't acted on?"
An internal email was sent in May 2025 - almost 12 months after the Covaris report was published - to senior NSW Health bureaucrats, including HNEH chief executive Tracey McCosker.
It requested approval to enact the report's recommendations to fix the HVAC system.
"Can you confirm how you would like the project to proceed with respect to actioning the recommendations in the Covaris report," the email said.
The Mater operates under a public-private partnership (PPP) between Novacare and NSW Health's Health Administration Corporation (HAC).
Under the PPP, Novacare subcontracts the hospital's maintenance to American corporate giant Honeywell.
HNEH acts as HAC "in administering the contract", and Ms McCosker is responsible for the contract's administration.
Hunter New England Health was contacted for comment.
While the HVAC system was found to need humidity control to prevent mould contamination, whistleblowers have told the inquiry that Honeywell failed to maintain the HVAC system properly.
Calvary Health Care's submission to the inquiry said it was "aware that there are significant issues with the HVAC systems throughout the hospital".
"Calvary has seen reports indicating that sections of piping have minimal or no water flow in the HVAC system and that the pipework is in a poor state," the submission said.
The submission added that there was "mould build-up and dirt debris" in the HVAC system.
"These factors create a stagnant environment resulting in bacterial growth and pose an unacceptable risk in a clinical environment."
Whistleblower Luke Carroll told the inquiry that "the core problem was wilful neglect".
"You didn't need to be a brain surgeon to recognise how dangerous that neglect could be in a medical setting," Mr Carroll said.
Mr Carroll, a former senior project manager for assets and infrastructure with Honeywell at the Mater, said "there was decaying and patched-over infrastructure, inadequate or non-existent maintenance practices, quite apparent falsification of maintenance records and what appeared to be a culture of deceptive conduct".
Honeywell and Novacare have denied the allegations.
An earlier Covaris report from March 2023, also commissioned by the NSW government, said "Novacare has not substantiated any evidence that the current HVAC systems have been maintained adequately".
In March, NSW Health Minister Ryan Park said "cladding on the hospital's external facade", which caused water leaks, was being replaced and work was "expected to be completed by mid-2027".
Mr Park said an independent assessment of the Mater's building infrastructure, including the HVAC system, was being done. The building audit is expected to be completed soon.
