Criteria air pollutants gases threaten both the public health and the public welfare, and that greenhouse gas emissions from motor vehicles contribute to that threat. This final action has two distinct 'findings,' which are: 1) The 'Endangerment Finding' in which the Administrator found that the mix of atmospheric concentrations of six key, well-mixed greenhouse gases threatens both the public health and the public welfare of current and future generations. These six greenhouse gases are: carbon dioxide (CO), methane (CH), nitrous oxide (NO), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF). These greenhouse gases in the atmosphere constitute the "air pollution" that threatens both
Nitrous oxide dominant. In a vacuum thruster, this may provide a monopropellant specific impulse ("I") of as much as 180 s. While noticeably less than the "I" available from hydrazine thrusters (monopropellant or bipropellant with dinitrogen tetroxide), the decreased toxicity makes nitrous oxide an option worth investigating. Nitrous oxide is said to deflagrate at approximately at a pressure of 309 psi (21 atmospheres). At 600 for example, the required ignition energy is only 6 joules, whereas at 130 psi a 2500-joule ignition energy input is insufficient. In vehicle racing, nitrous oxide (often referred to as just "nitrous") allows the engine to burn