The VOD concept is one of the key energy-saving principles in underground mine ventilation systems, and it can be applied across all mining commodities. VOD refers to the ability to deliver airflow specifically to the underground areas that require it. In other words, airflow is supplied only to the areas in need, while areas that do not require ventilation receive reduced airflow—or none at all. By implementing this principle, energy consumption from auxiliary fans can be significantly reduced. VOD consists of several levels of control strategies: User Control or Manual Control All ventilation devices—such as main fans, auxiliary fans, dampers, regulators, etc.—are operated manually. Time-Based Scheduling The second control strategy is time-based scheduling, which refers to the concept of triggering different setpoints for fans, regulators, and doors based on time inputs in accordance with a predefined schedule. Activity-Based Control The third strategy is activity-based control, as described by Tran-Valade and Allen (2013). This strategy is defined as the "automatic triggering of pre-defined actions in response to configured events." It can be summarized as an event-triggered function based on alternative inputs other than timers or environmental variables, each of which forms its own category. Similar to time-based scheduling, this control strategy applies the same event-triggering principle but is based on any available variable that can be integrated into the software. Tagging and Tracking This strategy requires the implementation of tag-and-tracking systems, with communication components integrated into the ventilation software. Airflow distribution in the mine is determined based on the location of personnel and equipment, as well as predefined rules for calculating the required airflow for each. Environmental-Based Control The fifth strategy is environmental-based control, which involves automated ventilation system adjustments based on real-time environmental data. This may include various sensor inputs such as gas, dust, diesel particulate matter (DPM), temperature (heat stress), etc., assuming that such sensors can operate underground and provide real-time data. Several components are needed to implement this principle effectively.