Sulphur hexafluoride (SF6)

The substance
At environmental temperatures sulphur hexafluoride is a colourless, odourless, non-toxic gas of high chemical stability and inertness. It is also non-flammable and about 5 times heavier than air - one of the heaviest known gases.

The major use of sulphur hexafluoride is in the electricity supply industry, where it is used as an electrical insulator in transformers and switch-gear, and in magnesium smelting because of its inertness. It also has some minor use in the semiconductor sector, as tracer gas for atmospheric analysis, in tennis balls, high performance vehicle tyres and in the cushioning soles of some trainers.

Major emissions
Sulphur hexafluoride is a man-made chemical not found naturally in the environment. The major sources of sulphur hexafluoride release include leakage from electrical switchgear, from magnesium smelting processes and use in semiconductor manufacture.

Impacts on human health and environment
Excessive exposure to sulphur hexafluoride may affect the brain. The main impact of sulphur hexafluoride on the environment is as a greenhouse gas, influencing climate change. Consequently sulphur hexafluoride is controlled under the Kyoto Protocol. Of the internationally monitored greenhouse gases it has by far the highest global warming potential (23,000 times that of carbon dioxide), however it is only released in small amounts. Due to its stability it has a very long atmospheric lifetime.

Emission to air reporting threshold: 50 kg/year

Data source: European Pollutant Emission Register