After opening their front door to see the hallway black with smoke, Mr de Boer headed for a ladder to the roof. He encouraged Ms Bignell to follow, but she was unable to do so because of her fear of heights.
"So I ended up running into the smoke and knocked on the neighbour's door, carried on to the end of the hallway to knock on the other guys' door ... and said 'there's a fire, get out'.
"I went to smash the fire alarm - those things are horrible to break - and I ended up taking a small gash out of my wrist."
When she flicked the alarm there was no response. "It's really silly. The fire alarms went off a month ago because of someone accidentally burning their roast ... This time when there was actually a fire, no smoke alarms went at all."
She and a neighbour, Jamie Whittaker, made it back to her flat and shut the door to keep out the smoke.
A group of people had gathered below their back window as she yelled that they were trapped.
Luckily, firefighters arrived with a ladder and carried them to safety.
Ms Bignell was taken to hospital and treated for smoke inhalation and a cut to her wrist, but later discharged.
Mr de Boer was convinced his partner saved lives. "She actually ran into the smoke - ran into the black - knocked on the neighbours' doors, in complete blackness.
"If it wasn't for her I don't think the neighbours would have made it out ... they would have been fast asleep, they wouldn't have known."
The Fire Service said the blaze was suspicious and referred it to police.
It appeared to have started in an apartment that should have been locked but wasn't, senior fire risk manager Mike McEnaney said.
The lack of a correctly operating fire system put residents at risk, he said. "There was no early warning or notification of a fire in the building and residents failed to be notified by fire alarms to evacuate the building until such time that there was a substantial fire developing."
He compared the incident to a fire at the nearby Heritage Hotel later in the day, where a "correctly operating" alarm system meant there was no risk to residents and minimal damage.
The manager of the Commerce St building, Jonathan Kim, said he had "no idea" who had the key to the empty apartment and the smoke alarms were tested every month.
More than 80 firefighters tackled the blaze and rescued four people, two from the roof. Two firefighters were treated at the scene for cuts and exhaustion.
