Abstract. There are few effective remedial strategies capable of reducing or preventing pollutant loads from underground mines. The Gas Redox and Displacement System (GaRDS) is a new approach devised for stabilising sulphide minerals by manipulating the atmosphere in mining voids. This prevention technique offers the potential for passive, low cost, and effective control of acid drainage from underground mines at sites where flooding is not feasible. GaRDS utilises reducing gas mixtures generated by anaerobic bacterial activity to displace oxygen without impeding drainage from the workings. These gas mixtures halt sulphide oxidation and acid generation, and can precipitate secondary sulphides from the accumulated drainage water. The GaRDS technique has significant advantages for mine operators who wish to temporarily close a mine, implement a low-cost, passive acid drainage prevention strategy, and retain the option of reopening the mine if metal prices increase. It is fully compatible with conventional ARD closure strategies for underground mines, and is expected to rapidly improve drainage water quality emerging from enclosures and prevent further sulphide oxidation. A field demonstration of the GaRDS technique has commenced at an adit in an historical mining district in Australia (Zeehan Mineral Field in Tasmania). The aim is to develop a generic technology that will find widespread application to both existing and historical acid drainage problems and prevent future problems arising at mine closure.