Six fire engines and around 40 firefighters were called to a fire in a laundry cupboard on the ground floor of a health club on Westbourne Grove in Notting Hill.
Firefighters were called when smoke was reported as coming out of an air conditioning vent in the building, three people left the building before the Brigade arrived.
The cause of the fire is believed to be an electrical fault in an air conditioning equipment.
The Brigade were called at 1324 and the fire was under control at 1432. Fire crews from Kensington Paddington, Hammersmith, Chiswick and Fulham fire stations attended the scene.