Six fire engines and around 40 firefighters were called to an outbuilding fire on the High Street in Harlington.
A single-storey outbuilding was destroyed by fire. One man was taken to hospital by London Ambulance Service crews.
Station Commander Andrew Allen, who was at the scene, said: “Crews were called to a fire in an outbuilding in a rear garden and worked swiftly to stop the fire from spreading to a nearby house.
“Firefighters removed and cooled two gas cylinders to an ambient temperature as some cylinders can explode when exposed to heat.”
The Brigade was called at 2339 and the fire was under control by 0131. Fire crews from Heathrow, Hayes, Feltham and Hillingdon fire stations attended the scene.
The Brigade’s Fire Investigators believe the fire was caused by an electrical fault.