Four fire engines and around 25 firefighters were called to a fire at a foundry (metal workshop) with offices above on Horton Close in West Drayton.
Part of the ground floor was damaged by fire. There were no reports of any injuries.
The fire was discovered by an employee in a neighbouring commercial unit when they could smell smoke and went outside to investigate. They then saw smoke coming from the side windows and called 999.
The Brigade was called at 2231 and the fire was under control by 2351. Fire crews from Hayes, Hillingdon, Heathrow and Feltham fire stations attended the scene.
The cause of the fire is under investigation.