St Kilda Station Officer Kate Hill said a male occupant left the bedroom where a candle was burning next to a bed, but when he returned moments later, the bed was on fire.
The man, a woman and a toddler were in the house at the time, but all managed to escape uninjured.
''It was lucky they were awake, because there was no smoke alarm in the house,'' she said.
When the emergency call came in about 11.50pm on Saturday, the fire was relatively contained, but by the time the fire brigade arrive three minutes later, the house was well alight, she said.
''The gentleman at the house said he didn't realise how fast the fire was, and I told him we're not making it up.
''Fire is fast; smoke alarms do save lives and just paying a wee bit more attention to ensure we have fire-safe practices can avoid people losing everything by something that could have been avoided.
''It's heart-breaking when things could be avoided, and it's just really lucky that these people were awake, because that fire happened so, so fast.''
A neighbour, who declined to be named, said the fire was spectacular.
''It was a real inferno - it was unreal. Thank God it wasn't windy because the house is only 2m away. My house would have gone up too.''
Ms Hill said the damage to the house was ''pretty significant'' and it was not known if the owners or the occupants had insurance.
''It's a timely reminder for everyone to ensure that they do follow fire-safe behaviour.
''If you don't have smoke alarms, get some. If you would like it checked, call the local fire station,'' she said.
''And if anyone wants more information about being fire-safe around the home, you can contact your local fire station for a free in-home fire safety check.''
Firefighters stayed at the scene for almost four hours.
