Ten fire engines and around 70 firefighters were called to a fire at a student accommodation block in Kingston Lane in Uxbridge.
A extraction system cupboard on the first, second and third floors of the building was damaged by fire.
Approximately 50 people left the building before the arrival of the Brigade. There were no reports of any injuries.
The Brigade was called at 1607 and the fire was under control at 1906. Fire crews from Hillingdon, Hayes, Southall, Northolt, Ruislip and other surrounding fire stations attended the scene.
The cause of the fire is believed to be accidental and due to an electrical fault