GC/MS stands for Gas Chromatograph Mass Spectrometry. In simple terms, a GC/MS separates an essential oil into individual components. The oil is vaporized upon entry into the device, and the oil passes through a column assisted by a carrier gas (usually helium or hydrogen). The column itself sits within an oven; here change in heat over time is managed. Different chemical compounds react at different speeds within the column, and this information is captured on the Gas Chromatograph Mass Spectrometry.