A GC/PID for automatic monitoring of BTEX in air, water and soils. This instrument uses a port valve with a single absorbent trap, and a 30 meter metallic 0.28 mm ID column. Minimum detection level as low as 10 ppt for application Benzene or 1,3-Butadiene in ambient air. Miniaturization, sensitivity, mobility and flexibility are its main features. Everything from the sample port up to the data storage is integrated in a 19`- rack 5U.