INTRUDERS set fire to a building used by a firm to test fire extinguishers.
The arsonists broke into the building owned by Nu-Swift on the Lowfields Business Park in Elland at 6pm on Thursday. They set fire to wood in a room.
People working at another business nearby saw the smoke and called firefighters.
Watch manager Peter Rushby, of Huddersfield fire station, said: "The room was enclosed and had no windows.
"It was lucky the fire was spotted at an early stage and we were able to confine it to that room."