Reducing Sulfur Hexafluoride (SF6) Emissions from Gas-Insulated Switchgear (310 CMR 7.72)

SF6 is a strong greenhouse gas (GHG), with a global warming effect nearly 24,000 times greater than carbon dioxide. SF6 also lasts in the atmosphere for more than 3,000 years after it is released.

As an excellent insulator, SF6 is often found in gas-insulated switchgear (GIS), equipment used in high-voltage electrical systems to control the flow of electrical current. SF6 routinely leaks into the atmosphere from closures and joints in GIS equipment. 

Regulatory Requirements

SF6 is used to insulate certain high-voltage electrical equipment called gas-insulated switchgear (GIS). This equipment is used in large electricity generation, transmission, and distribution facilities, not in homes or other types of businesses.

Specifically, the regulation defines GIS to include “switches, stand-alone gas-insulated equipment, and any combination of electrical disconnects, fuses, electrical transmission lines, transformers and/or circuit breakers used to isolate gas-insulated electrical power system equipment.”

Companies and municipalities that own, lease, operate, or control gas-insulated switchgear (GIS) that contains SF6 and is located in Massachusetts are required to comply with 310 CMR 7.72. The regulation refers to these entities as “GIS owners” and includes the following requirements.

For GIS purchased after January 1, 2015:

  • The GIS owner must ensure that the GIS has a maximum annual SF6 leak rate of 1%, as represented by the GIS’s manufacturer (310 CMR 7.72(4)(a)).
  • GIS owners must maintain their GIS in accordance with maintenance procedures or industry best practices that have the effect of reducing leakage of SF6 (310 CMR 7.72(4)(b));
  • If, beginning with the second time that a GIS owner adds SF6 to a GIS unit, or group of commonly-owned, leased, operated, or controlled GIS, the GIS owner becomes aware that the annual average leakage rate for the new GIS equipment is greater than 1%, the GIS owner must inform MassDEP and describe actions that are expected to reduce the emission rate in the future (310 CMR 7.72(4)(c)); and
  • All GIS owners must record, no less than annually, the amount of SF6 added to each piece of active GIS equipment (310 CMR 7.72(8)(b)).

See below for MassDEP Leak Rate Exceedance and Annual Reporting forms.

Regardless of GIS purchase date:

  • Upon removal of any GIS containing SF6 from the ownership, lease, operation, or control of a GIS owner, the GIS owner must provide for the secure storage, re-use, recycling, or destruction of the SF6 (310 CMR 7.72(4)(d)).

Under 310 CMR 7.72(5&6), the two largest electric distribution utilities in Massachusetts, because they are subject to federal GHG reporting requirements, must also:

  • Meet an annually declining emission limit that reaches 1% or less by 2020;
  • Report SF6 emissions from GIS to MassDEP each year; and
  • Limit aggregate, company-wide SF6 emissions to the company-specific limits stipulated in the regulation at 310 CMR 7.72(5)(b).

Additional Resources

Reporting Forms

You may fill out and save Microsoft Word forms on your computer. PDF versions need to be printed out and completed by hand.

Additional Resources

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