The Dorrance Colliery's mine fan complex spanned the history of the colliery. The oldest fan, an 1883 cast iron and wood Guibal, is the last known survival of the most common type used in the anthracite region. Its 35-foot diameter span, while not unique, was the largest of the fans found in the coalfields. Not only was the fan in good condition, it still was connected to its original power source - an 1883 horizontal slide valve steam engine. In addition to the Guibal fan, the Dorrance fan complex housed two other fans and the remains of their steam engines. One was a 1908 28-foot Dickson-Guibal fan powered by a Corliss steam engine, the other a c. 1930 Duplex Conoidal fan and Corliss steam engine. The Dorrance fan complex - its fans, engines and buildings - represented the technological development of mine ventilation. The complex was identified as the most complete mine ventilation system in the anthracite region.