Coal seam gas has historically been and still remains a major issue for underground Illawarra Coal’s mining operations in the Southern Coalfield. The control of seam and strata gas is essential to maintaining operational safety and mining continuity. The Resource and Exploration department surface exploration drilling program is currently investigating coal seam gas characteristics through the use of coal permeability testing (injection fall-off testing). The need for coal permeability testing is essential for assessing the reservoir gas characteristics in the seams. Coal seam structure and reservoir properties are closely related to regional and localised geological structure, which greatly influence insitu coal seam permeability and reservoir characteristics. Testing is conducted on all seams within the mining stress relaxation envelope of the mined seam. Specialist software (PAN Systems) is used to process the data and interpretation is undertaken in conjunction with all other available data-sets. Permeability testing is critical for understanding the gas regimes within Illawarra Coal’s four mining lease areas. Permeability data is needed for the Bulli through to the Tongarra coal seams primarily for mine gas drainage, evaluation of Coal Bed Methane production potential of deeper seams in the Illawarra Coal Measures and identification of zones of variable gas drainability and outburst potential.