Auxiliary ventilation systems are generally used to ventilate development sections or dead-end headings. The air is moved from a fresh air source, normally a trunk intake airway, to a point close to the face of the heading and back out; hence two air routes are required. Typically in mining, auxiliary fan and duct systems are used to provide a second air route within the primary development airway/roadway. Click here to learn more about modelling of auxiliary ventilation systems.
Thanks for the share, PMJ!