An experimental study of the decomposition of acetaldehyde in a dry air mixture has been carried out using a dielectric barrier discharge. Operating parameters that affect the CH3CHO destruction efficiency include the gas mixture composition, the applied voltage, and the gas residence time in the reactor. The plasma is produced in a narrow gap by a dielectric barrier discharge at low applied voltage, 40 kHz. An isotopic labeling (CD3CHO) is used with gas chromatography-mass spectrometry identification of the formed stabilized species in order to investigate the mechanism of acetaldehyde decomposition, and especially the CH3• radical stability. Additionally, the influence of the plasmagen gas mixture composition on the chemical reaction pathways in the discharge has been studied.