There are several types of ventilation systems in mining, each designed to move air safely and efficiently through underground workings. Although every mine is unique, most systems can be described in terms of primary versus secondary ventilation, forcing versus exhaust layouts, and special configurations such as booster fan systems and ventilation on demand. Understanding these categories helps engineers select the right combination of mine ventilation fans, shafts and ducts for a given orebody and mining method.
The first distinction is between primary and secondary (auxiliary) ventilation. Primary ventilation is the main system that moves large quantities of air through shafts, declines, main intakes and returns. It is normally driven by one or more large axial or centrifugal fans at the surface or in main fan stations underground. The primary circuit supplies air to multiple levels, districts and production areas and carries contaminated air back to exhaust points.
Secondary or auxiliary ventilation covers local systems that provide airflow to headings, blind drives, stopes and other locations not directly served by the primary airways. Auxiliary ventilation uses smaller axial fans, flexible or steel ducts and sometimes small booster fans. Forcing auxiliary systems push fresh air to the face, while exhaust auxiliary systems draw contaminated air away. These systems are frequently moved as development advances and must be carefully managed to maintain air quantity and quality at the working face.
Mine ventilation systems can also be classified as forcing, exhaust or mixed systems. In a forcing system, main fans pressurize intake airways and push air into the mine, with returns flowing towards unguided exhaust openings. In an exhaust system, main fans draw air from return airways, pulling fresh air into the mine through intakes at near-atmospheric pressure. Many modern mines use mixed systems that combine aspects of both, optimizing gas control, leakage patterns and fan efficiency.
Another important type is the booster fan system. In deep or extensive mines, primary fans alone may not be able to overcome network resistance economically. Booster fans installed in main branches or sub-levels increase pressure and airflow to distant or high-resistance districts. Booster systems require careful design to avoid recirculation and to maintain stable airflow directions under different operating conditions.
With advances in automation, many operations are adding ventilation on demand (VOD) on top of conventional systems. VOD automatically adjusts fan speeds, starts and stops auxiliary fans, and changes regulator settings based on where people and equipment are working and on measured gas and temperature conditions. This allows mines to maintain safe ventilation while reducing energy consumption for large mine fans and auxiliary systems.
In summary, the main types of ventilation systems in mining are primary and secondary circuits, forcing and exhaust layouts, booster fan arrangements and modern ventilation on demand strategies. All of them depend on correctly selected and positioned mine ventilation fans, well-designed airways and consistent operational control.
