There are many different types of extraction methods available. Some of the most common extraction methods are steam distillation (used to produce certain essential oils), cold pressing (used to extract the oil from citrus peels), the solvent extraction method, and the supercritical carbon dioxide extraction method. Each of these extraction methods will result in a significant difference in the purity of the product and will also change the profile of all other compounds found within that oil. Before inhalable products are marketed, laboratories need to perform analytical testing to identify any residual solvents, pesticides, or any other contaminants.