When people talk about the five types of ventilation, they are usually grouping different ways of moving air into and out of buildings, factories and underground mines. The names vary between standards, but a practical classification includes natural ventilation, general mechanical ventilation, local exhaust ventilation, balanced ventilation and ventilation with heat or energy recovery. Each type plays a different role in controlling air quality, heat and contaminants.
Natural ventilation relies on wind and temperature differences rather than fans. Air enters and leaves through openings such as windows, vents and shafts, driven by pressure differences. In mines, natural ventilation pressure arises from density differences between intake and return shafts. On its own, natural ventilation is unpredictable and rarely sufficient for modern industrial or mining operations, but it still influences how air moves and can assist or oppose mechanical systems.
General mechanical ventilation uses fans to supply or exhaust air for an entire space. Examples include roof and wall fans in factories, main ventilation fans in mines and tunnel fans in underground road systems. These systems dilute contaminants and control temperature across large areas, rather than capturing pollutants at a single point. They may be exhaust-only, supply-only or partly balanced.
Local exhaust ventilation (LEV) targets contaminants at the source. Hoods, enclosures and capture devices are connected to ductwork and fans that remove dust, fumes or vapours directly from the process. LEV is widely used above welding stations, crushers, mixers and chemical tanks. By capturing pollutants “at the hood”, it reduces worker exposure and the load on general ventilation.
Balanced ventilation uses both supply and exhaust fans to control where air enters, where it leaves and how pressure is distributed. In industrial buildings this prevents uncontrolled infiltration and allows clean rooms or control rooms to be kept slightly positive while dirty areas are kept slightly negative. In mines, primary (main) and auxiliary ventilation are combined to create balanced airflow patterns that deliver fresh air to faces and route return air safely to exhaust points.
Ventilation with heat or energy recovery (HRV/ERV) is an evolution of balanced mechanical ventilation. Exhaust and supply air streams pass through a heat exchanger so that energy is recovered from the outgoing air and used to precondition the incoming air. This reduces heating or cooling loads while maintaining fresh air supply. Although best known in building HVAC, the same principle can be used in industrial plants to capture waste heat from exhaust streams.
In summary, the five types of ventilation can be viewed as natural ventilation, general mechanical ventilation, local exhaust ventilation, balanced mechanical ventilation and ventilation with heat or energy recovery. Effective mining and industrial ventilation strategies often combine several of these types to achieve safe, efficient control of air quality and temperature.
