Six fire engines and around 40 firefighters attended a fire at a block of flats on Lamb Close in Northolt.
Most of a first-floor flat in a four-storey block was damaged by fire. One person was taken to hospital by London Ambulance Service to be treated for smoke inhalation.
The Brigade's Control Officers received the first of 22 calls at 0502 and crews from Southall, Northolt, Hillingdon and Ruislip fire stations were mobilised to the scene. The fire was brought under control by 0611.
The cause of the fire is under investigation.