Four fire engines and around 25 firefighters were called to a fire in a block of flats in Bath Street, Islington.
A two-roomed flat on the second floor was damaged by fire. Around 16 people left the property before the arrival of the Brigade. A woman was rescued by firefiighters wearing breathing apparatus, using a smoke hood, and a man was led to safety by crews via the building's internal staircase.
Fire escape hoods can provide up to 15 minutes of protection from four of the main fire gases and filter toxic smoke.
A man and woman were taken to hospital and another woman was treated on scene by London Ambulance crews
The Brigade was called at 1837 and the fire was under control by 1943.
Fire crews from Shoreditch, Whitechapel, Dowgate and Islington Stations attended the incident.
The cause of the fire is believed to be the unsafe disposal of smoking materials.