Firefighters from Kingswood and Brislington fire stations were alerted by a neighbour who heard a smoke alarm sounding in the house.
When crews arrived they found smoke coming from the letterbox, but as they were unable to get a response, they forced their way in through the front door.
Firefighters in breathing apparatus made a search of the home where they found a man in his 50s asleep in an upstairs bedroom. He was walked to safety before being treated by paramedics for the effects of smoke inhalation.
The source of the smoke was found to be cooking which had been left on a hob in the kitchen. The small fire caused smoke to fill the property.
An Avon Fire & Rescue Service spokesman said: “The incident highlights the importance of a working smoke alarm, which alerted neighbours to the fire. This allowed the man to be rescued with just minor smoke inhalation, averting a much more serious incident.”
Smoke alarms are provided free of charge as part of the fire safety visit service.