Sulphur hexafluoride (SF6) is an extremely effective electrical insulant and has very significant advantages over alternative materials. It is non-flammable, a critical requirement in the high-voltage applications for which we use it, and because of its effectiveness, takes up less volume than an equivalent insulating volume of an oil alternative. Equipment filled with SF6 can leak and requires replacement.
SF6 is a greenhouse gas and one tonne is equivalent to approximately 23,900 tonnes of carbon dioxide.
Reported gas loss, as an absolute amount and (percentage of inventory) was14.7 tonnes (2.6%) in 2008/09 compared with 18.8 tonnes (3.5%) in 2007/08.
There has been no increase in our inventory due to the acquisition of KeySpan, so direct comparison with previous years is possible.