Due to the more and more common use of siloxanes in consumer products and various industries, there has been an increase of their concentration in biogases produced from sewage sludge and municipal waste and, consequently, in the soil, water, and air. This paper presents sources and mechanisms of siloxane migration to the environment, characterizes types and products of their transformations in the atmospheric air and during the combustion of biogas, assesses hazards posed to the atmospheric air, and presents the results of siloxane concentration measurements in biogases and the atmospheric air. It draws attention to the new problems that have emerged in toxicology and atmosphere protection, outlines directions for necessary research, proposes ways to reduce emissions of volatile methyl siloxanes (VMS), and suggests the introduction of relevant legislation.