Four fire engines and around 25 firefighters were called to a fire on Chiswick High Road in Chiswick.
Half of a ground floor bedsit was damaged by the fire. There were no reports of any injuries.
The Brigade was called at 1614 and the fire was under control by 1655. Fire crews from Chiswick, Acton, Southall and Hammersmith fire stations attended the scene.
The Brigade's fire investigators believe the most likely cause of the fire was a halogen lamp coming into contact with skirting and flooring.