Duct Runs : Ducts are hollow tubes running from manhole to manhole inside a conduit in an underground system. They are of various sizes usually from 2 to 6 inches in diameter
US Department of Labor, Electric Power eTool: Glossary of Terms, Occupational Safety & Health Administration OSHA, Washington, D.C., USA 2010. https://www.osha.gov/SLTC/etools/electric_power/gl ossary.html, (OSHA/ Electr Pwr - Amer) {618}