The Greenhouse Gas Protocol (GHG Protocol) offers the most widely used greenhouse gas accounting standards. Its Corporate Standard, specifically, provides standards and guidance for companies and other types of organisations preparing a GHG emissions inventory. It covers the accounting and reporting of the six greenhouse gases covered by the Kyoto Protocol — carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulphur hexafluoride (SF₆).