Eight fire engines and around 60 firefighters tackled a fire in a flat on Clayton Road, Hayes.
Part of a flat on the first floor of a mixed use block was damaged by fire. Most of a third-floor terrace was also damaged by the blaze. There were no reports of any injuries.
The fire is believed to have been caused by the unsafe disposal of smoking materials on a terrace with timber decking.
A London Fire Brigade spokesperson said: “We’d rather you didn’t smoke at all, but if you are 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 1708 and the fire was under control by 1827. Fire crews from Hillingdon, Southall, Chiswick, Northolt and surrounding fire stations were at the scene.