Brisbane firefighters have determined a candle in a bedroom caused a massive apartment blaze in Fortitude Valley on the weekend.

The fire on Sunday destroyed several units in the building.

Queensland Fire and Rescue Service assistant commissioner Ian Mitchell says a woman is lucky to have survived the inferno.

He says she was sleeping in the unit that caught fire and was unconscious when the building's manager Todd Raumer dragged her to safety.

"I'd have to commend the efforts of Todd Raumer, he was the building manager," he said.

"He carried the lady from the fifth floor all the way to the ground.

"Before that he'd taken the firefighters up to show us where the fire was, and then carried the lady down where she was taken by the ambulance."