IEC and Australian Standards Information on SF6 Gas

SF6 gas has a negligible impact on the environment according to Australian and International Standards (IEC 1634:1995 and AS2791-1996).

The standards do not consider SF6 to be an ozone depletion gas because the catalytic reaction scheme associated with these types of gases is practically impossible with SF6 for the following two reasons:

"- due to the structure of its ultraviolet absorption spectrum, SF6 is not photolysed in the critical ozone destruction altitude range between 32km and 44km, so that very little atomic fluorine is expected to come from SF6;"

"- due to the high chemical affinity of fluorine to hydrogen, which is abundantly present in the stratosphere, any atomic fluorine that may have been produced from SF6 would rapidly be neutralised by the formation of HF using the hydrogen atoms available from water molecules which are present at a concentration of 10,000 ppmv." (IEC 1634:1995, P135).

Because of these two factors the Standard concludes that: "Taking account of the facts that one Cl atom can catalytically destroy 10,000 ozone molecules, that the concentration of SF6 is 1000 times lower than that of CFC and that virtually no free fluorine is formed from SF6 according to the circumstances as described, it is clear that SF6 does not contribute to the destruction of stratospheric ozone." (IEC 1634:1995, P135).

As a greenhouse gas, SF6 also has a negligible impact. The contribution due to SF6 is one part in more than 10,000 compared with the contribution of the other agents and is therefore negligible.

As a result, the standards conclude that: "the substantial amount of evidence available indicates that SF6 has a negligible impact on the global environment." (IEC 1634:1995, P137).