Head space analysis is basically a technique where the vapors in the gas above, and in equilibrium with a solid or liquid is sampled, as opposed to sampling, solely, the solid or the liquid themselves. The advantage of this approach is that gas chromatography can be used as the analytical technique, as opposed to liquid chromatography, thus providing four to five orders of magnitude greater sensitivity. The procedure involves the extraction of a volume of the equilibrium gas over the sample (usually about 10 ml) by a syringe through a vial containing a bed of an appropriate absorbent. The vial is the placed in line with a gas chromatography column, the vial heated and the vaporized sample swept on the column and the components separated. This technique has been used to identify spoiled food, fragrances from botanical material, the determination of plasticizers in plastics and for forensic samples involving arson.