Most of our essential oils are obtained by steam distilation which is the most traditional technique to produce natural essential oil.
Each essential oil should pass our test of Gas Chromatography-Mass Spectrometry and the relevant compounds have to reach the level required by International Standards for high quality of therapeutic essential oils.
Eg: Our tee-tree oil has more than 40% of terpinen-4-oil & 3% of 1.8-Cineol. The international standard ISO 4730 (2004) and the identical Australian standard AS 2782-2009 (“Oil of Melaleuca, Terpinen-4-ol type”) define that the chemical composition of tee-tree oil should have a minimum of 30% of terpinel-4-ol & a maximum of 15% for 1.8-Cineol. (http://www.teatree.org.au/standards.php)
Besides, as we understand that different chemotypes of essential oils give different aromatherapeutic effects, we only choose the one which represents the most powerful healing properties and which is suitable for everyone.