Four fire engines and 21 firefighters and officers were called to a fire at plant hire yard in Mollison Avenue, Enfield.
Three mini diggers were gutted in the blaze.
The fire is believed to have been caused by a fault in a diesel compressor.
The Brigade was called at 1957 and the fire was under control at 2117. Fire crews from Chingford, Edmonton and Woodford fire stations attended the scene.