Four fire engines and around 25 firefighters were called to a fire at a flat on Homefield Road in Bromley.
A flat on the second floor and a balcony on the third floor of a five-storey block were destroyed by the fire. One man left the affected flat before the arrival of the Brigade and was taken to hospital by London Ambulance Service crews suffering smoke inhalation.
Firefighters rescued a man and a woman from the flat above via a ladder. They were assessed at the scene by London Ambulance Service crews. Another woman was led to safety by crews using a fire escape hood. She was also assessed on scene.
Control Officers also gave advice over the phone to reassure two people in another flat, who were unaffected by the fire.
Station Commander Nathan Hobson, who was at the scene, said: "Firefighters were faced with a well developed fire on arrival. There was a lot of smoke coming from the building which prompted multiple calls from members of the public to our Control Room.
"Crews worked hard to bring the blaze under control."
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 15 calls to the fire.
The Brigade was called at 0901 and the fire was under control by 1030. Fire crews from Bromley, Beckenham and Lee Green fire stations were at the scene.
The cause of the fire is under investigation.