A kitchen and living room went up in flames after a cooler set on fire.
Two fire crews from Preston were called to the semi-detached home on Howarth Road, Preston at around 3.30pm today.
Crew manager Rob Barker said: "This was an unusual fire because the smoke alarms went off and no-one reported it.
"The cooler had set on fire and although it had caused extensive damage to the kitchen and living room, it burnt itself out because of the lack of oxygen.
"We attended but didn't have to do much. We just used our thermal imaging camera to make sure the fire was out.
"The occupant was at work but did everything right. The smoke alarm went off but no-one reported it because there were no signs from the no signs from the outside.
"If it had been during the night the alarm would have been vital. I would also say that you should turn applicances off you're not using but this was not one of those."