Six fire engines and around 40 firefighters were called to a fire at a maisonette on Norman Crescent in Hounslow.
A split-level maisonette on the ground and first floors of the building was destroyed by fire. Half of the second floor of another split-level maisonette and part of the third floor were also damaged by fire.
Firefighters wearing breathing apparatus rescued one man from the maisonette on the ground floor of the building using a fire escape hood. Three adults and a child were rescued from the maisonette on the second floor of the building. One man was treated on scene by London Ambulance Service crews.
Fire escape hoods provide members of the public with up to 15 minutes protection from four of the main fire gases (carbon monoxide, hydrogen cyanide, hydrogen chloride and acrolein) and can be worn by conscious or unconscious people. If more than 15 minutes protection is required then another hood can be given to each wearer. They do not provide oxygen but temporarily filter toxic smoke to make breathing easier.
The Brigade's 999 Control Officers took 13 calls to the fire and gave vital fire survival guidance to residents inside the flat on how to stay safe before crews arrived.
Station Commander Dan Johnson said: "On arrival, crews encountered a fully developed fire involving two flats over four floors.
"They worked extremely hard to rescue five members of the public and contained the fire to the flats involved, preventing fire spread to other flats."
The Brigade was called at 1757 and the fire was under control by 1913. Fire crews from Feltham, Heston, Heathrow, Heston, Hayes and Hillingdon fire stations attended the scene.
The cause of the fire is under investigation.