You do not choose high or low static pressure in isolation; the “right” static pressure is the value your ventilation system actually needs at the required airflow. A well designed fan selection matches fan pressure capability to system resistance so that the fan delivers the target volume efficiently, without wasting power or creating excessive noise.
Static pressure represents the resistance of the system: friction in ducts, fittings, filters, coolers, silencers and, in mining, long drifts, raises and regulators. For a given airflow, there is a specific static pressure requirement. If the fan cannot reach this pressure, airflow will be too low and the space, process or mine heading will be under-ventilated. In that case you need a fan with higher static pressure capability.
However, more pressure than the system needs is not automatically better. If you install a high static pressure fan on a very low-resistance system, it will tend to move more air than necessary, increasing noise and energy consumption. Often operators then partly close dampers to reduce flow, which simply wastes the extra pressure as heat across the restrictions. The result is a more expensive fan and motor, higher running costs and no real improvement in ventilation quality.
In industrial plants and underground mines, engineers therefore focus on matching the fan curve to the system curve. The system curve shows how much pressure is required at different flows. The fan curve shows how much pressure the fan can develop at those flows. The intersection of the two is the operating point. You want a fan whose operating point sits near the required airflow and pressure, preferably in the high-efficiency region of the fan curve, with a reasonable safety margin for fouling, future duct changes or mine development.
In summary, you usually want neither unnecessarily high nor insufficiently low static pressure. You want the amount of static pressure that matches your ductwork or mine airway resistance at the design airflow, with enough margin to stay reliable but not so much that you pay for unused capability and extra noise.
