Around 100 people were alerted to a fire at their student accommodation building on Chalk Farm Road, NW1, thanks to a smoke alarm sounding.
Watch Manager David Waters, who was at the scene, said: “This incident shows just how important it is to have working smoke alarms.
“Smoke alarms give the earliest possible warning when a fire starts Make sure smoke alarms are fitted in rooms where a fire can start except kitchens or bathrooms where heat alarms are more appropriate..”
A small part of a studio flat was damaged by fire.
The Brigade was called at 1837 and the fire was under control at 2007. Four fire engines and around 25 firefighters from Kentish Town, Euston, and Soho fire stations attended the scene.
The cause of the fire is believed to be due to an electrical fault in a bathroom extractor fan.