In this paper, we report the chlorine gas sensing using the conducting polymer polyaniline (PANI) as an active layer, which is incorporated in fluorinated ethylene propylene (FEP). The sensor film was made by grafting acrylic acid onto FEP. This grafting was carried out using gamma rays on the film, which was then sulphonated using concentrated H 2 SO 4 . Finally aniline was polymerized onto this film resulting into FEP-g-AA-SO 3 H/PANI. The film of FEP-g-AA-SO 3 H-PANI was found to be selectively sensing chlorine with sensitivity of 45–50% at low ppm levels.