Four fire engines and around 25 firefighters were called to a fire at a block of flats on Turkey Street in Enfield.
A storage room on the ground floor was completely destroyed by fire.
One woman evacuated before the Brigade arrived and was treated on the scene for smoke inhalation by London Ambulance Service.
The Brigade was called at 1502 and the incident was under control by 1557. Crews from Enfield, Edmonton, Chingford and Tottenham fire stations were in attendance.
The cause of the fire is under investigation by the Brigade and Met police.