Ventilation fans provided fresh air for miners deep within the mines. Ventilation pipe connected to fans carried air wherever it was needed in the mine to provide miners with breathable air by diluting and displacing dust and noxious gases. Fans were designed to run continuously with little or no maintenance. Fans were normally mounted on platforms well clear of the mine entrance and far away from equipment traffic so as to provide the cleanest and coolest air possible. The examples are centrifugal fans, also known as radial fans. The rotation of an impeller within the casing caused air to travel through it in a radial direction, developing air pressure as it did so. These two examples are rather simple in design, as they do not provide for speed or air volume control. Electricity to power ventilation fans was a major cost factor, accounting for as much as one-third of the electrical power for a typical underground mine. These fans were used in the Guadalupe mine from the 1940s until the mine closed in the 1970s. The Guadalupe Rubbish Company donated the fans to NAQCPA in 1987.