Four fire engines and around 25 firefighters were called to a garage alight on Rosebery Road in Hounslow.
A garage at the rear of a house was destroyed by the fire. Two cylinders exploded due to the heat before the Brigade arrived and the window of a nearby property was damaged by flying debris. A man and woman were treated on scene for minor smoke inhalation.
The Brigade's 999 Control Officers took 25 calls to the fire.
The Brigade was called at 1130 and the fire was under control by 1251. Fire crews from Heston, Twickenham and Hillingdon fire stations were at the scene.
The cause of the fire is under investigation.