Occupational hazards and other problems related to the use of sulfur hexafluoride in metalclad substations

This paper is both a review and a detailed analysis of present knowledge of the possible risks of asphyxiation and intoxication inherent in the operation of SF5 substations and maintenance of electrical switchgear. The first part of the study, the danger of asphyxiation in SF5 substations, is based on the physical properties of this gas with regard to flow and diffusion. The diffusion of SF5 into air as a function of time was calculated and the curves obtained provide a clear illustration of the tendency of this heavy gas to stagnate in low areas and the consequent risks of asphyxiation faced by personnel in such places. In a second part, the problem of the decomposition of S Fa in electrical switchgear leading to the formation of several irritant or toxic products is discussed together with the undesirable influence that certain contaminants, such as humidity, have on promoting decomposition. Several examples of the types of incident that can occur with SF6-insulated equipment are described and discussed.