Four fire engines and around 25 firefighters tackled a fire on Mandeville Road in Northolt.
Most of an external storage area and a small part of an adjoining office were damaged by the fire. Five people left the building before the Brigade arrived. There were no reports of any injuries.
The fire is believed to have been accidental and was caused by the failure of a smart gas meter.
Control Officers took the first of eight calls at 0951 and mobilised crews from Wembley and Northolt fire stations to the scene. The incident was over for firefighters at 1059.