Compared with other gas-phase analytes, the coexistence and competing effect of moisture component has long faced great difficulty and technical challenge for the reliable detection of chemically oxidizing active H₂O₂ vapor (HPV). Recently, our group designed and prepared a chemiresistive sensor based on conductive films of poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and PEDOT:PSS/PEDOT to achieve direct detection of HPV at ppm level. Specially, the hydrophobic PEDOT layer was polymerized on the surface of the PEDOT:PSS film by electrochemical method to attenuate the adverse effect of moisture within HPV on the stability and detection performance of the sensing film of PEDOT:PSS/PEDOT.