Firefighters from Clapham Fire Station led a man to safety from a fire at a maisonette in Union Grove, Clapham.
He had been alerted to the fire by working smoke alarms in his home and was taken to hospital by London Ambulance Service.
The Brigade was called at 1122 and the fire was under control by 1246.
Ten firefighters and two fire engines attended the incident, with crews using hose reels, breathing apparatus and a thermal image camera.
The fire destroyed more than half of the four roomed maisonette, which was spread over the fourth and fifth floors of a block of flats. The cause of the fire is under investigation.