Carbon offset production flows to regions or industries that have a lower price of carbon—unless carbon can be purchased from that area, which offsets effectively permit, equalizing the price. Carbon offsets may represent six primary categories of greenhouse gases: carbon dioxide (), methane (CH), nitrous oxide (NO), perfluorocarbons (PFCs), hydrofluorocarbons (HFCs), and sulfur hexafluoride (SF). Carbon offsets have several common features: In 2009, 8.2 billion metric tons of carbon dioxide equivalent changed hands worldwide, up 68 per cent from 2008, according to the study by carbon-market research firm Point Carbon, of Washington and Oslo. But at EUR94 billion, or about $135 billion,
Nitrous oxide and retains adequate mental faculties to respond to questions and instructions from the dentist. Inhalation of nitrous oxide is used frequently to relieve pain associated with childbirth, trauma, oral surgery, and acute coronary syndrome (includes heart attacks). Its use during labour has been shown to be a safe and effective aid for birthing women. Its use for acute coronary syndrome is of unknown benefit. In Britain and Canada, Entonox and Nitronox are used commonly by ambulance crews (including unregistered practitioners) as a rapid and highly effective analgesic gas. 50% nitrous oxide can be considered for use by trained non-professional first