Thir report deals with the use ot SF6 gas and those of its chemical derivatives which are produced in switchgear and controlgear during normal service and under certain abnormal conditions. Two main aspects are covered: - the effects on humans of exposure to SF6 and its decomposition products; - the effects on the environment of SF6 and its decomposition products. The risks associated with contact with SF6 gas and suitable precautions are discussed for each stage in the normal life cycle of an item of equipment and under abnormal conditions. This publication has the status of a Technical Report - type 2.