4. Conclusions In this paper, an analytical method has been optimised to determine 54 volatile organic compounds in air by TD–GC/MS. The method presents good recoveries for all compounds. The linearity in the responses andtherepeatability forall compounds is alsogood.Theanalysisofblanksshowedthepresenceofsome compoundsofinterest,mainlybenzeneandtoluene,whichaffect the detection limits for these compounds. However, the high levels of these compounds in real samples mean that the method can be useful for determining them. Urban samples measured in Tarragona city have made it clear that traffic emissions affect VOC levels. The variability