Computer software has been developed to link real time information generated by underground mine ventilation airflow monitoring sensors into a network simulation program to undertake network simulations and allow interpretation of key system data and operational changes. Results were used in the development of a computerized monitoring and simulation system to provide immediate or real time data on air behaviour within each branch within an underground mine ventilation network through linking of sensors to the ventilation network simulation software. The outcome of the project is an online system which can report changes in the mine ventilation system, allow causes of changes to be isolated and rectified, improve balancing of available air throughout the mine, allow improved approaches to regulator setting and dispense with much of the labour used for underground ventilation measurement. The main work activities involved in the research program have involved examination and modelling of regulators used in two Australian mining (coal and metalliferous) environments, software modification and considerable mine site testing and optimising activities. The mathematical modelling of airflow through a variety of mine regulators was an important part of the project and this aspect is discussed. There is some discussion on approaches to control of flow through ventilation systems with increased information. 2 THEORY OF REGULATORS A regulator can be described as a large thin plate with an orifice installed in a fluid conduit. When a difference in pressure exists between the two sides fluid flows in the pattern shown in Figure 1. On the low pressure side the fluid issues as a converging jet in line with the centre of the orifice. The jet converges to its smallest area at a distance of about half the orifice diameter (Le Roux, 1990). This area is called the “vena contracta” (Ac at Fig. 1). The ratio between vena contracta and orifice area is the “coefficient of contraction”, Cc (Ac/Ar at Fig. 1). Figure 1. Airflow pattern through an orifice (after Burrows et al, 1989). McElroy (1935) found that the Cc value is a relation between the ratio of the orifice and airway cross sectional area, N (Ar/A at Fig. 1). Bernoulli’s equation can be applied to both sides of the orifice as shown in Figure 1 in order to calculate the velocity and hence the airflow quantity. A correction must be made for the contraction of the jet at the vena contracta. The velocity equated based on Bernoulli’s equations is the velocity at the vena contracta. Therefore, the velocity at the orifice can be obtained with the following equation: