The fire was started by a toaster in the kitchen of a house at 5 Old Bridge Rd sometime on Friday but was not noticed until shortly after 4pm.
The toaster had been put away in a cupboard with a roller door that, when closed, came into contact with the switch and caused the appliance to turn on and continue toasting.
A statement released by the brigade yesterday said that caused the inside of the cupboard to heat up, eventually starting a fire.
The home owners were out of town and so the fire developed unnoticed, spreading to the kitchen and several other rooms before smoke was noticed by a neighbour.
The owners have agreed to open the house this weekend as they believe it holds an important safety message.
Between 1pm and 3pm on Sunday, the fire brigade will be at the house to guide members of the public through, highlighting stages of the fire spread and providing relevant fire safety advice.
''It will graphically demonstrate the importance of closing doors in buildings and show how several rooms next to the kitchen were undamaged because the owners simply had closed the doors,'' the statement said.
Station Officer Shane Ryan said it was important that people turned off all electrical appliances that are put inside these or similar type cupboards at the wall socket.
''It is also possible to install an electrical cut-off switch that is fitted to the cupboard roller door to prevent this type of incident occurring.''
There have been three similar incidents over the past few years in Alexandra, two of which resulted in fires that caused substantial structural, heat and smoke damage to the homes involved.
Deputy Chief Fire Officer Mark Hutton issued a reminder - ''ensure that every home has working photo-electric long life battery smoke alarms fitted to each sleeping area and other rooms throughout homes''.
