ROCKFORD (WIFR) -- The Rockford Fire Department was dispatched to Blue Water Thermal at 5136 27th Avenue on August 10, for a commercial structure fire. A fire in the duct work from a heat-treating machine was reported as well as smoke coming from the roof and overhead door. Crews on the inside were able to gain access to the duct work and extinguish the fire. The fire was caused by oil that accumulates in the duct work. The fire was deemed accidental and it has been estimated that $1,000.00 has been lost. Luckily, the duct work is the only thing that was damaged.