A reversible axial fan should run in reverse only when the ventilation system has been specifically designed to change airflow direction, and the fan itself is rated for bidirectional operation. This is common in tunnels, underground mines and some process plants where airflow may need to be reversed for safety or operational reasons.
In tunnel ventilation and smoke control, reversible axial fans are often installed so that airflow can be directed either toward or away from a fire or construction zone. During normal operation, the fan runs in its primary direction to provide fresh air and dilute vehicle exhaust. In an emergency, the control system may command the fan to reverse, directing smoke in a controlled direction to create safe escape routes and assist firefighting. These reversible fans are specially designed with blade profiles, motors and controls that allow effective operation in both directions.
In underground mines, reversible axial fans may be used to change the main airflow direction in certain shafts or to handle special operating modes. For example, reversing flow can help manage gas layering, clear smoke after a fire, or adapt ventilation to changing development patterns. However, such changes must always be approved in the mine ventilation plan and carefully controlled to avoid creating unsafe conditions elsewhere in the network.
Reversible axial fans can also be used for periodic cleaning or de-icing. Running the fan in reverse at reduced speed for a short period can help dislodge dust deposits on filters or louvers and prevent ice build-up in cold climates. This should be done according to manufacturer recommendations to avoid overloading the fan or causing damage.
It is important to note that not every axial fan can simply be reversed by changing motor rotation. Many standard axial fans are optimised for one direction and are not structurally or aerodynamically suitable for reverse operation. Attempting to run a non-reversible fan backwards may greatly reduce airflow, increase noise and vibration, and overstress blades or hubs. Only fans specifically rated as reversible, with suitable blade profiles and hub designs, should be operated in both directions.
From a system perspective, running a reversible fan in reverse should be coordinated with damper positions, doors, regulators and other fans. If other equipment is not adjusted accordingly, reversing one fan may create unexpected recirculation paths or undesirable pressure zones. Control logic and operating procedures must therefore be clearly defined and tested.
In summary, a reversible axial fan should run in reverse when the ventilation system requires a controlled change in airflow direction, such as in tunnels, mines and smoke-control systems, or during specific cleaning or de-icing cycles. The fan must be designed for bidirectional operation, and system controls must be configured so that reversing the fan maintains safe and effective ventilation.
