Whilst not common, underground mines with high elemental sulphur content (as distinct from mines with high fine-grained sulphide content) create a range of unusual ventilation-related issues. The key hazards include: (elemental sulphur) dust explosions (primary and secondary), fires and burning (with emission of heat and sulphur dioxide gas), reactions with nitrates used in explosives, hazards due to corrosion, generation of hydrogen sulphide gas and acid water, and pyrophoric reactions between the elemental sulphur and naked iron (e.g. ground support or underground infrastructure) or other metals including silver and copper. Elemental sulphur will form explosive mixtures in air at lower dust concentrations and at lower temperatures than the more common sulphide dust explosions. This paper, based on a case study, discusses these issues and causal mechanisms and potential ventilation controls required to minimise the risks from mining ores with high elemental sulphur content.
