Four fire engines and around 25 firefighters were called to a flat fire on Grove Lane in Kingston.
Half of a flat on the second floor of a three-storey block was damaged by the blaze.
Around five people left the block before the arrival of the Brigade. There were no reports of any injuries.
Station Commander Stephen McGhie, who was at the scene said:
“Firefighters arrived to find a smoke logged flat and a large fire in the bedroom. Crews worked extremely hard to prevent the fire from damaging the roof and spreading to neighbouring flats.
“Smoke alarms were fitted, however they did not activate at the time of the fire.
“Homes need multiple smoke alarms or you won’t be properly covered.
“Ideal spots for smoke alarms include rooms where you leave electrical equipment running like satellite boxes, computers or heaters; any room where you smoke, and anywhere you charge your mobile or laptop.”
The Brigade was called at 1545 and the fire was under control by 1644. Fire crews from Kingston, Surbiton, and New Malden fire stations attended the scene.
The Brigade's fire investigators believe the fire was caused by a fault in an immersion heater in a boiler.