Firefighters are urging people to ensure they fully extinguish their cigarettes after a Holloway flat fire on Cornwallis Square in Islington.
Half of the room on the first floor was damaged by the blaze. A man from the adjacent flat was treated on scene by London Ambulance Service crews.
The Brigade’s fire investigators believe the fire was 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 as you don’t know what it may land on which could potentially start a fire."
The Brigade was called at 0653 and the fire was under control by 0751. Fire crews from Holloway, Kentish Town, Islington and Hornsey fire stations attended the incident.