SF6 is a very powerful insulator and has been widely used as an insulating medium in high voltage electrical equipment for decades. It is stable, non-toxic and has low flammability, all of which make it suitable for a variety of operating environments and voltage levels in the power industry.

What are the effects of SF6?

According to an online calculator developed by the Environmental Protection Agency, each pound of SF6 released into the atmosphere is equivalent to the annual carbon emissions of two cars on the road, or 1,100 gallons of gasoline, or 11,000 pounds of coal burned. And because it's so stable -- meaning it doesn't mix with other compounds -- it stays in the atmosphere for a long time, about 3,200 years. Methane, by contrast, stays in the environment for only about 12 years.

Estimates of how much SF6 is emitted each year vary widely. But measurements of its presence in the atmosphere suggest it is growing - from four parts per trillion in 2000 to around one part per trillion in 2021.