About SF6 gas

SF6 gas – the facts

SF6 is a synthetic compound consisting of one sulphur atom and six fluorine atoms and does not normally occur in nature. SF6 is gaseous at room temperature and is heavier than air. Due to the strong bonds between the sulphur and fluorine atoms SF6 is inert under normal circumstances. This gas has certain electrical properties that make it suitable as insulation and switching medium in switchgear for power distribution. SF6 breaks down into toxic substances on incineration, for example when an internal arc occurs in the switchgear. In the event of such an internal arc SF6 gas and its toxic by-products are released into the atmosphere. These reactions also occur in normal use whenever an arc is suppressed. The toxic residues will then remain in the housing, as a result of which special precautions are required when dismantling and recycling the system at the end of its service life.

Switchgear with SF6 gas

There are three principal designs for SF6 insulated switchgear. With the first two, known as controlled pressure systems and closed pressure systems, release of SF6 is unavoidable in practice. This is because the systems require maintenance in the course of their service life, at which point leakage occurs. Furthermore, leakage occurs when the units are dismantled at the end of their service life. The third principle design is the hermetically sealed system, which does not require maintenance in the course of its service life. Emissions of these systems due to leakage are claimed to be limited although these will never be zero, as in practice gaskets are a source for leakage. Leaks can also not be ruled out in the long term over the service life of the installation (> 30 years).

Annual worldwide emission of SF6 gas

As energy consumption increases the use of SF6 increases in absolute terms as well. It is estimated that annual SF6 gas production will reach around 8000 metric tonnes, 80% of which is used in electrical energy technology for switching operations, cooling and insulation [1].

The production of SF6 is still increasing, despite the fact that the gas is included in the Kyoto protocol for its contribution to the greenhouse effect. Studies have shown that the annual percentage increase of SF6 gas in the air is 8% +/- 0.7%, the highest figure of all greenhouse gases [2]. With the increase in the number of switchgear using SF6 gas for switching and insulation purposes in electricity networks, emissions of SF6 gas into the atmosphere will increase accordingly, a trend which will continue if policy remains unchanged.


1. Smythe, K. “Trends in SF6 and End-Use Applications: 1961-2003”, Conference on SF6 and the Environment. Scottsdale, Arizona, December 1-3, 2004.

2. Powell, A.H. “Environmental aspects of the use of Sulphur Hexafluoride. ERA Technology Ltd. 2002”.

Green switching supporters

The following organisations are supporters and contributors to the Green Switching Forum.