Four fire engines and around 25 firefighters were called to a fire at a commercial unit on Romford Road in Forest Gate.
Part of a single storey unit was damaged by the fire. One man left the building before the Brigade arrived. He was treated at the scene for smoke inhalation by London Ambulance Service crews and taken to hospital.
The Brigade's 999 Control Officers took nine calls to the blaze.
The Brigade was called at 1120 and the fire was under control by 1221. Fire crews from Stratford, Plaistow, Barking and Ilford fire stations were at the scene.
The cause of the fire is under investigation.