The ACT Coroner’s Court also heard ductwork in Flint Restaurant was too thin and filled with combustible material when the fire broke out in June 23 last year.

The restaurant, Parlour Wine Room and upstairs offices were torched during the spectacular blaze; the neighbouring Diamant Hotel was also damaged.

Counsel assisting the Coroner, Anthony Williamson, told the inquiry a key issue would be whether the exhaust system ductwork complied with Australian building standards.

Fire investigators were called in to survey the damage and determined the fire started in the ductwork.

Anthony Walker, ACT Fire and Rescue senior firefighter and qualified fire investigator, said yesterday a spray mechanism designed to cool rogue embers or timber from the gas-fired pizza oven was offline.

‘‘In your opinion, based on your experience, had that spray mechanism been operational on the afternoon of June 23, do you think this fire would have occurred?’’ Mr Williamson asked.

‘‘If it’s doing what the manual says it’s supposed to be doing then if it had been operational I don’t think this fire would have occurred,’’ Mr Walker replied.

The court also heard investigators found grease remnants in the back of the pizza oven, and the contracted cleaner complained he was hampered by a lack of access points.

Mr Walker said the ductwork should have had four access points — investigations revealed none. They also found combustible material in the system, and the cleaner told investigators he pulled out one or two garbage bags of matter two days before the fire.

‘‘What it essentially meant was that the ductwork would have had enough material in there, [grease and material], that there could have been a possible fuel source within the area,’’ Mr Walker said.

The witness said the ductwork was only a single-sheet thick, rather than the preferred double or triple-sheet thickness. Molonglo Group’s Andrew Cox, was at his desk — directly above Flint’s kitchen — on the afternoon of the fire when he heard a rumbling from within the floor.

Mr Cox told the inquiry he felt the ‘‘light tremor’’, and then heard the fire alarm.

Firefighters Peter Fitzpatrick and Anthony Wilson were the first to enter the building, armed with breathing apparatuses, and started to attack the fire with a wall-fixed hose.

They went back downstairs to get a more powerful hose, but when they returned to the upper level the fire had ‘‘developed considerably’’, with flames in the ceiling above them.

The pair made the decision to retreat out of the building just as their supervisor, Station Officer Bruce Rodway, ordered them back out of concern for their safety.

Several witnesses either said no sprinkler system was triggered or they couldn’t recall whether a sprinkler system was triggered.

Mr Rodway also said a workman from the adjacent Nishi construction site approached him at the scene and mentioned fire hydrants on the western side of the pavilion had been ‘‘disconnected or isolated’’.

But the experienced firefighter said there was still an adequate water supply to combat the blaze.

The inquiry before Chief Coroner Lorraine Walker continues.