On February 25, 2010, the California Air Resources Board adopted a regulation to limit and monitor sulfur hexafluoride (SF6) emissions from electric power sector equipment. SF6 is a highly inert and non-corrosive gas, and because of these properties it is used in small amounts as insulation for high-voltage switchgear, which are components of the electrical transmission and distribution system. The measure was developed in consultation with electric utility representatives and is expected to achieve a 70 percent reduction of SF6 emissions statewide from electrical utilities – a total reduction of 250,000 metric tons of carbon dioxide equivalent by 2020.
The measure takes effect January 1, 2011, and from 2011 to 2020, it ratchets down the allowable SF6 emission rate from 10 percent in 2011 to 1 percent in 2020. The emission rate is the percentage of total SF6 that grid equipment is designed to use for insulation that can be emitted each year.