Wisconsin issued an emergency rulemaking, effective January 2, 2011, to incorporate Greenhouse Gases (GHGs) into the Wisconsin Administrative Code. Specifically, the Wisconsin Administrative Code is revised to define "greenhouse gases", which includes carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), sulfur hexafluoride (SF6), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs). Construction permit applications for major sources and major modifications at major sources must address emissions of GHGs (see related discussion on EPA's Tailoring Rule below). Further, projects with potential to emit increase of GHG emissions of 75,000 tons per year (on a CO2 equivalent basis) could be required to determine Best Available Control Technology (BACT) for GHGs. The Wisconsin Administrative Code also establishes global warming potential (GWP) factors which are used to calculate individual GHG emissions on a CO2 equivalent basis.