Four fire engines and around 25 firefighters tackled a fire at a sewage works on Mogden Lane in Isleworth.
There were no reports of any damage or injuries.
The cause of the fire is believed to have been a small explosion within an electrical substation.
The Brigade was called at 1103 and the fire was under control by 1234. Firefighters from Heston, Twickenham and Feltham fire stations are attending the scene.