Four fire engines and around 25 firefighters were called to a fire at a block of flats on Hanbury Road in Acton.
A small part of a bedroom and balcony in a third floor flat was destroyed by fire. Four women left the flat before the Brigade arrived and were treated on scene for smoke inhalation by the London Ambulance Service.
Fire investigators believe the fire was accidental and most likely caused by the unsafe disposal of smoking materials.
A London Fire Brigade spokesperson said: "If you're a smoker, it’s absolutely vital you ensure your cigarette is completely out when you’ve finished smoking it.
“If you don’t, you risk causing a fire which could not only destroy your home, but also cost you your life.”
The Brigade was called at 0314 and the incident was over by 0422. Crews from Acton, Chiswick, Ealing and Park Royal fire stations were in attendance.