Four fire engines and around 25 firefighters were called to a fire on Weymouth Road in Hayes.
A garage at the rear of a semi-detached house was destroyed by the fire. A man was taken to hospital by London Ambulance Service crews and a woman was treated at the scene.
Firefighters cooled and removed two cylinders which were involved in the fire as some cylinders can explode when exposed to heat.
The Brigade was called at 1321 and the fire was under control by 1421. Fire crews from Southall, Hillingdon, Northolt and Hayes fire stations were at the scene.
The fire is believed to have been accidental and caused by an unknown electrical event.