Longwall bleeder and gob areas have long been one of the most challenging and uncertain areas in a ventilation model. There is a tendency to "black box" the bleeder and gob areas in a model, however this can lead to problems when examining the addition of contaminates in the air stream as they pass though these undefined areas. Additionally, the interaction between the bleeders and the gob is important to understand when attempting to control gas concentration at bleeder evaluation and mixing points. This paper discusses several experiences and common problems encountered with developing an accurate model to represent bleeder and gob areas. Common techniques used to quantify the bleeder systems and the shortcomings associated with these techniques are also discussed.
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