Four fire engines and around 25 firefighters tackled a fire at a seven-storey block of flats on Abbey Road in Barking.
Part of a first-floor flat was damaged by fire, along with most of the flat's balcony. One man was taken to hospital by London Ambulance Service to be treated for smoke inhalation.
The fire is believed to have been caused by the unsafe disposal of smoking materials.
A London Fire Brigade spokesperson said: "If you smoke it is vitally important you stub it right out, preferably in an ashtray.
"Always ensure your cigarette is completely out when you’ve finished smoking it. If you don’t, you risk causing a fire.
"Firefighters recommend that you have a look at our online Home Fire Safety Checker to make sure there are no hidden hazards in your home.
"The online tool will ask you a series of questions that will help us work out the level of risk in your home, or the home of someone you care for. It only takes a few minutes to get tailored advice to keep yourself and loved ones safe from fire.”
The Brigade received the first of 12 calls at 1351 and Control Officers mobilised crews from East Ham, Ilford, Plaistow and East Greenwich fire stations to the scene. The fire was extinguished by 1449.