Dairy manure storage is a nutrient efficient and environmentally friendly way to allow recycling of the manure by field application during the growing season. During storage, bacteria and other anaerobic processes breakdown the manure and reform them into noxious compounds, such as ammonia, carbon dioxide, methane, and hydrogen sulfide (H2S). The characteristics and concentration risk levels of these manure gases are described. This fact sheet focuses on the hazards associated with H2S and the best management practices to maintain farm safety around manure storage and handling systems.