Two fire engines and around 10 firefighters were called to a fire at a maisonette on Petersfield Avenue, Romford.
A small section of a first and second floor maisonette was damaged by fire.
Firefighters wearing breathing apparatus used a fire escape hood to lead one woman to safety via an internal staircase. She was treated at the scene for smoke inhalation and taken to hospital 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 was called at 0330 and the fire was under control at 0458. Fire crews from Harold Hill and Romford fire stations attended the scene.
The cause of the fire is under investigation.