Global Warming Solutions Act of 2006 a 30% reduction statewide, with mandatory caps beginning in 2012 for significant emissions sources. The bill also allows the Governor to suspend the emissions caps for up to a year in case of emergency or significant economic harm. The State of California leads the nation in energy efficiency standards and plays a lead role in environmental protection, but is also the 12th largest emitter of carbon worldwide. Greenhouse gas emissions are defined in the bill to include all of the following: carbon dioxide, methane, nitrous oxide, sulfur hexafluoride, hydrofluorocarbons and perfluorocarbons. These are the same greenhouse gases listed in Annex
Sulfur hexafluoride with satisfactory accuracy at very low concentrations, and the Earth's atmosphere has a negligible concentration of . Sulfur hexafluoride was used as a non-toxic test gas in an experiment at St. John's Wood tube station in London, United Kingdom on 25 March 2007. The gas was released throughout the station, and monitored as it drifted around. The purpose of the experiment, which had been announced earlier in March by the Secretary of State for Transport Douglas Alexander, was to investigate how toxic gas might spread throughout London Underground stations and buildings during a terrorist attack. Sulfur hexafluoride is also routinely