Hypercritical Carbon Dioxide Extraction: This is a relatively new process. The hypercritical temperature of carbon dioxide is 33 degrees centigrade, at which point it has features of both liquid and gas. At this temperature it is a very good solvent for essential oils. Because the temperature is relatively low there is no risk of heat damage to the oil. There is no chemical reaction between the carbon dioxide and the oil when it is evaporated off and it leaves no traces of contamination. The one problem is that the process requires to be carried out under very high pressure (200 Atmospheres) and this requires very heavy and expensive equipment. As yet, only tiny amounts of oil have been extracted in this way, but it is seen by many as having potential to produce very pure oils in the future.

Many aromatherapists are not happy to use essential oils extracted by exsisting means of solvent extraction, because of the potential for the oil to be contaminated by the chemicals used in the extraction process.