Jet fans are extensively used in civil road tunnels, large enclosures (such as underground car parks) and other applications requiring the movement of air in large low-pressure voids but are rarely systematically used in underground mining. Despite a relatively low cost and compact size compared to typical mine axial fans, jet fans have found little practical use in most mines, apart from occasional use in coal and room and pillar mines. Jet fans have very limited pressure capabilities and are inefficient in moving airflow through higher-resistance airways.
The paper explores the technical merits of jet fans for new applications in mining environments and highlights areas where the fans may be highly beneficial compared to conventional fans or ventilation controls such as louvres or doors. Jet fans can excel in applications that benefit from producing targeted ventilation flows while allowing unrestricted vehicle movement that would otherwise be hindered by doors or ventilation controls.
An overview of the theory and application of jet fans in mining environments is provided and examples and theoretical effectiveness of potential uses in ramp flow control and block cave extraction ventilation is researched using modelling software. Further detailed design and practical test work for specific applications is intended for future research.

While mine ventilation systems may account for 40% to 50% of the energy consumption of a mine operation, auxiliary ventilation alone may be accountable for half of this consumption. In effect, auxiliary ventilation systems comprise a significant portion of a mine operation's base energy demand and is consequently responsible for a large percentage of the total mine operating costs.
While modern duct-fan systems require precise engineering design, meticulous attention to installation and regular maintenance practices, many installations are often designed based on outdated rules of thumb and with disregard to best installation practices.
Over twelve years of investigations of duct-fan systems, the author has found them to be, in general, fairly energy inefficient, with many systems operating at efficiencies below 65% and with air leakages ranging between 25% and 75%.
This paper presents how engineering design principles can be applied to design efficient and reliable auxiliary ventilation systems, especially focusing on assemblage losses. Case studies are presented to demonstrate the effect of design, installation and maintenance practices on system reliability and operating costs. In particular, the effect of assemblage losses (screen, inlet bell, elbows, couplings, duct outlet, etc.) is quantified in terms of operating efficiencies, energy consumption and costs.

Numerous instances of the word "efficiency" in fan system evaluation contribute to unclear application of efficiencies in simulations and for power estimation. Ventilation simulations using "fixed flows" and software default fan efficiency values to specify fan duties may result in omission of fan system component losses and under-estimation of required fan pressure and absorbed power. Numerous factors contribute to the overall efficiency of a given fan system, considering aerodynamic and motor/drive components along with factors such as the inlet and diffuser components, silencers, dampers, duct transitions, and/or unfavorable velocity distribution (incompletely developed flow profiles) at the fan inlet or outlet. In this study, the authors review measured operating points of 84 unique main and booster fan installations to determine typical fan system efficiencies. The study discusses how data were measured, reflects on the limitations of in-situ measurements, and compares the differences between fan systems at coal, metal, and nonmetal operations.