An air sampling and analytical method based on adsorption on porous polymer “Tenax TA” followed by automatic thermal desorption “ATD” and GC/MS analysis was developed for ten pesticides commonly used on major crops in Britanny and some of their metabolites in air “from spray drift and volatilisation transfer processes”: alachlor, atrazine “and two major degradation products: deethylatrazine and deisopropylatrazine”, carbofuran, cyprodinil, epoxyconazole, iprodione “and 3,5-dichloroaniline”, lindane “and -HCH, its isomer”, metolachlor, terbuconazole and trifluralin. This method was established with special consideration for optimal thermal desorption conditions, linear ranges, limits of detection and quantification. Moreover, collection efficiencies of Tenax TA at room temperature were examined. This method was then applied to the determination of ambient pesticide levels during the spraying season at a rural area. The method was also applied to determine the vertical gradient of alachlor concentrations on a treated maize parcel to evaluate volatilisation fluxes.