Four fire engines and around 25 firefighters were called to a fire at a flat on Upper Richmond Road West in Richmond.
Part of a four-roomed flat on the ground floor was damaged by the blaze. Three people left before the Brigade arrived. There were no reports of any injuries.
The Brigade was called at 0237 and the fire was under control by 0333. Fire crews from Richmond, Chiswick, Wandsworth and Kingston fire stations attended.
The fire is believed to have been caused by a fault in the boiler.