Cryogenic processes capitalize on the fact that methane and nitrogen change phase (from gas to liquid) at different temperatures. By manipulating and controlling the pressures and temperatures in the system, the methane is liquefied and collected as it drops out of the gas. The gas is then re-vaporized, yielding a sales stream with nitrogen levels that conform to pipeline quality standards. The excess nitrogen is either flared or vented to the atmosphere. Because of the temperatures involved (-240 to -250 degrees), the long cool down time and extensive equipment required, cryogenic systems are most often used for large projects where processing volumes exceed five million cubic feet per day and in those instances where nitrogen levels range from 30% to 40% or higher. The low temperatures allow the plant to recover over 90% of the ethane in the natural gas. Most new gas processing plants use cryogenic recovery technology.