Firefighters spent 40 minutes tackling a blaze at a wood merchants.
They were called to the timber yard in Twitty Fee, Danbury, at 6.34am this morning and found an extractor unit alight.
The fire was extinguished by 7.15am but the two crews remained on scene to ensure no hotspots remained.
An investigation will be carried out to establish the cause of the incident.
It was the incident dealt with by working crews during a two hour strike by FBU members this morning.