A method for dielectrically insulating active electric parts A method for dielectrically insulating an active electric part wherein the electrical active part is arranged in a gas-tight housing comprising an insulating gas which contains or consists of a compound of formula (i) Rf1-(O)x-Rf2 wherein Rf1 and Rf2 are identical or different and designated fluorocarbon residues having a H/F ratio of equal to or less than 0.5 and x is 1, 2, or 3.