Six fire engines and around 40 firefighters were called to a fire in a basement car park with shops and flats above on Parchmore Road in Thornton Heath.
Rubbish in the stairwell of the underground car park was damaged by fire.
Firefighters assisted a man and a woman to safety. They were both treated for smoke inhalation and the man was taken to hospital by London Ambulance Service crews. A further eight people self-evacuated with other residents remaining in their unaffected flats.
The fire is believed to have been accidental and caused by smoking.
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 properties but also cost you your life."
The Brigade was called at 0959 and the fire was under control by 1153. Crews from West Norwood and surrounding fire stations were at the scene.